* [RFC PATCH 0/4] Fast noirq bulk page allocator
@ 2017-01-04 11:10 ` Mel Gorman
0 siblings, 0 replies; 26+ messages in thread
From: Mel Gorman @ 2017-01-04 11:10 UTC (permalink / raw)
To: Jesper Dangaard Brouer; +Cc: Linux Kernel, Linux-MM, Mel Gorman
This series is motivated by a conversation led by Jesper Dangaard Brouer at
the last LSF/MM proposing a generic page pool for DMA-coherent pages. Part of
his motivation was due to the overhead of allocating multiple order-0 that
led some drivers to use high-order allocations and splitting them which
can be very slow if high-order pages are unavailable. This long-overdue
series aims to show that raw bulk page allocation can be achieved relatively
easily without introducing a completely new allocator. A new generic page
pool allocator would then ideally focus on just the DMA-coherent part.
The first two patches in the series restructure the allocator such that
it's relatively easy to build a bulk page allocator. The third patch
alters the per-cpu alloctor to make it exclusive to !irq requests. This
cuts allocation/free overhead by roughly 30% but it may not be noticable
to anyone other than users of high-speed networks (I'm not one). The
fourth patch introduces a bulk page allocator with no in-kernel users as
an example for Jesper and others who want to build a page allocator for
DMA-coherent pages. It hopefully is relatively easy to modify this API
and the one core function to get the semantics they require. Note that
Patch 3 is not required for patch 4 but it may be desirable if the bulk
allocations happen from !IRQ context.
include/linux/gfp.h | 23 ++++
mm/page_alloc.c | 329 ++++++++++++++++++++++++++++++++++++----------------
2 files changed, 254 insertions(+), 98 deletions(-)
--
2.11.0
--
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^ permalink raw reply [flat|nested] 26+ messages in thread
* [PATCH 1/4] mm, page_alloc: Split buffered_rmqueue
2017-01-04 11:10 ` Mel Gorman
@ 2017-01-04 11:10 ` Mel Gorman
-1 siblings, 0 replies; 26+ messages in thread
From: Mel Gorman @ 2017-01-04 11:10 UTC (permalink / raw)
To: Jesper Dangaard Brouer; +Cc: Linux Kernel, Linux-MM, Mel Gorman
buffered_rmqueue removes a page from a given zone and uses the per-cpu
list for order-0. This is fine but a hypothetical caller that wanted
multiple order-0 pages has to disable/reenable interrupts multiple
times. This patch structures buffere_rmqueue such that it's relatively
easy to build a bulk order-0 page allocator. There is no functional
change.
Signed-off-by: Mel Gorman <mgorman@techsingularity.net>
---
mm/page_alloc.c | 126 ++++++++++++++++++++++++++++++++++----------------------
1 file changed, 77 insertions(+), 49 deletions(-)
diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index 2c6d5f64feca..d8798583eaf8 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -2610,68 +2610,96 @@ static inline void zone_statistics(struct zone *preferred_zone, struct zone *z,
#endif
}
+/* Remote page from the per-cpu list, caller must protect the list */
+static struct page *__rmqueue_pcplist(struct zone *zone, unsigned int order,
+ gfp_t gfp_flags, int migratetype, bool cold,
+ struct per_cpu_pages *pcp, struct list_head *list)
+{
+ struct page *page;
+
+ do {
+ if (list_empty(list)) {
+ pcp->count += rmqueue_bulk(zone, 0,
+ pcp->batch, list,
+ migratetype, cold);
+ if (unlikely(list_empty(list)))
+ return NULL;
+ }
+
+ if (cold)
+ page = list_last_entry(list, struct page, lru);
+ else
+ page = list_first_entry(list, struct page, lru);
+
+ list_del(&page->lru);
+ pcp->count--;
+ } while (check_new_pcp(page));
+
+ return page;
+}
+
+/* Lock and remove page from the per-cpu list */
+static struct page *rmqueue_pcplist(struct zone *preferred_zone,
+ struct zone *zone, unsigned int order,
+ gfp_t gfp_flags, int migratetype)
+{
+ struct per_cpu_pages *pcp;
+ struct list_head *list;
+ bool cold = ((gfp_flags & __GFP_COLD) != 0);
+ struct page *page;
+ unsigned long flags;
+
+ local_irq_save(flags);
+ pcp = &this_cpu_ptr(zone->pageset)->pcp;
+ list = &pcp->lists[migratetype];
+ page = __rmqueue_pcplist(zone, order, gfp_flags, migratetype,
+ cold, pcp, list);
+ if (page) {
+ __count_zid_vm_events(PGALLOC, page_zonenum(page), 1 << order);
+ zone_statistics(preferred_zone, zone, gfp_flags);
+ }
+ local_irq_restore(flags);
+ return page;
+}
+
/*
* Allocate a page from the given zone. Use pcplists for order-0 allocations.
*/
static inline
-struct page *buffered_rmqueue(struct zone *preferred_zone,
+struct page *rmqueue(struct zone *preferred_zone,
struct zone *zone, unsigned int order,
gfp_t gfp_flags, unsigned int alloc_flags,
int migratetype)
{
unsigned long flags;
struct page *page;
- bool cold = ((gfp_flags & __GFP_COLD) != 0);
-
- if (likely(order == 0)) {
- struct per_cpu_pages *pcp;
- struct list_head *list;
-
- local_irq_save(flags);
- do {
- pcp = &this_cpu_ptr(zone->pageset)->pcp;
- list = &pcp->lists[migratetype];
- if (list_empty(list)) {
- pcp->count += rmqueue_bulk(zone, 0,
- pcp->batch, list,
- migratetype, cold);
- if (unlikely(list_empty(list)))
- goto failed;
- }
-
- if (cold)
- page = list_last_entry(list, struct page, lru);
- else
- page = list_first_entry(list, struct page, lru);
- list_del(&page->lru);
- pcp->count--;
+ if (likely(order == 0))
+ return rmqueue_pcplist(preferred_zone, zone, order,
+ gfp_flags, migratetype);
- } while (check_new_pcp(page));
- } else {
- /*
- * We most definitely don't want callers attempting to
- * allocate greater than order-1 page units with __GFP_NOFAIL.
- */
- WARN_ON_ONCE((gfp_flags & __GFP_NOFAIL) && (order > 1));
- spin_lock_irqsave(&zone->lock, flags);
+ /*
+ * We most definitely don't want callers attempting to
+ * allocate greater than order-1 page units with __GFP_NOFAIL.
+ */
+ WARN_ON_ONCE((gfp_flags & __GFP_NOFAIL) && (order > 1));
+ spin_lock_irqsave(&zone->lock, flags);
- do {
- page = NULL;
- if (alloc_flags & ALLOC_HARDER) {
- page = __rmqueue_smallest(zone, order, MIGRATE_HIGHATOMIC);
- if (page)
- trace_mm_page_alloc_zone_locked(page, order, migratetype);
- }
- if (!page)
- page = __rmqueue(zone, order, migratetype);
- } while (page && check_new_pages(page, order));
- spin_unlock(&zone->lock);
+ do {
+ page = NULL;
+ if (alloc_flags & ALLOC_HARDER) {
+ page = __rmqueue_smallest(zone, order, MIGRATE_HIGHATOMIC);
+ if (page)
+ trace_mm_page_alloc_zone_locked(page, order, migratetype);
+ }
if (!page)
- goto failed;
- __mod_zone_freepage_state(zone, -(1 << order),
- get_pcppage_migratetype(page));
- }
+ page = __rmqueue(zone, order, migratetype);
+ } while (page && check_new_pages(page, order));
+ spin_unlock(&zone->lock);
+ if (!page)
+ goto failed;
+ __mod_zone_freepage_state(zone, -(1 << order),
+ get_pcppage_migratetype(page));
__count_zid_vm_events(PGALLOC, page_zonenum(page), 1 << order);
zone_statistics(preferred_zone, zone, gfp_flags);
@@ -2982,7 +3010,7 @@ get_page_from_freelist(gfp_t gfp_mask, unsigned int order, int alloc_flags,
}
try_this_zone:
- page = buffered_rmqueue(ac->preferred_zoneref->zone, zone, order,
+ page = rmqueue(ac->preferred_zoneref->zone, zone, order,
gfp_mask, alloc_flags, ac->migratetype);
if (page) {
prep_new_page(page, order, gfp_mask, alloc_flags);
--
2.11.0
^ permalink raw reply related [flat|nested] 26+ messages in thread* [PATCH 1/4] mm, page_alloc: Split buffered_rmqueue
@ 2017-01-04 11:10 ` Mel Gorman
0 siblings, 0 replies; 26+ messages in thread
From: Mel Gorman @ 2017-01-04 11:10 UTC (permalink / raw)
To: Jesper Dangaard Brouer; +Cc: Linux Kernel, Linux-MM, Mel Gorman
buffered_rmqueue removes a page from a given zone and uses the per-cpu
list for order-0. This is fine but a hypothetical caller that wanted
multiple order-0 pages has to disable/reenable interrupts multiple
times. This patch structures buffere_rmqueue such that it's relatively
easy to build a bulk order-0 page allocator. There is no functional
change.
Signed-off-by: Mel Gorman <mgorman@techsingularity.net>
---
mm/page_alloc.c | 126 ++++++++++++++++++++++++++++++++++----------------------
1 file changed, 77 insertions(+), 49 deletions(-)
diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index 2c6d5f64feca..d8798583eaf8 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -2610,68 +2610,96 @@ static inline void zone_statistics(struct zone *preferred_zone, struct zone *z,
#endif
}
+/* Remote page from the per-cpu list, caller must protect the list */
+static struct page *__rmqueue_pcplist(struct zone *zone, unsigned int order,
+ gfp_t gfp_flags, int migratetype, bool cold,
+ struct per_cpu_pages *pcp, struct list_head *list)
+{
+ struct page *page;
+
+ do {
+ if (list_empty(list)) {
+ pcp->count += rmqueue_bulk(zone, 0,
+ pcp->batch, list,
+ migratetype, cold);
+ if (unlikely(list_empty(list)))
+ return NULL;
+ }
+
+ if (cold)
+ page = list_last_entry(list, struct page, lru);
+ else
+ page = list_first_entry(list, struct page, lru);
+
+ list_del(&page->lru);
+ pcp->count--;
+ } while (check_new_pcp(page));
+
+ return page;
+}
+
+/* Lock and remove page from the per-cpu list */
+static struct page *rmqueue_pcplist(struct zone *preferred_zone,
+ struct zone *zone, unsigned int order,
+ gfp_t gfp_flags, int migratetype)
+{
+ struct per_cpu_pages *pcp;
+ struct list_head *list;
+ bool cold = ((gfp_flags & __GFP_COLD) != 0);
+ struct page *page;
+ unsigned long flags;
+
+ local_irq_save(flags);
+ pcp = &this_cpu_ptr(zone->pageset)->pcp;
+ list = &pcp->lists[migratetype];
+ page = __rmqueue_pcplist(zone, order, gfp_flags, migratetype,
+ cold, pcp, list);
+ if (page) {
+ __count_zid_vm_events(PGALLOC, page_zonenum(page), 1 << order);
+ zone_statistics(preferred_zone, zone, gfp_flags);
+ }
+ local_irq_restore(flags);
+ return page;
+}
+
/*
* Allocate a page from the given zone. Use pcplists for order-0 allocations.
*/
static inline
-struct page *buffered_rmqueue(struct zone *preferred_zone,
+struct page *rmqueue(struct zone *preferred_zone,
struct zone *zone, unsigned int order,
gfp_t gfp_flags, unsigned int alloc_flags,
int migratetype)
{
unsigned long flags;
struct page *page;
- bool cold = ((gfp_flags & __GFP_COLD) != 0);
-
- if (likely(order == 0)) {
- struct per_cpu_pages *pcp;
- struct list_head *list;
-
- local_irq_save(flags);
- do {
- pcp = &this_cpu_ptr(zone->pageset)->pcp;
- list = &pcp->lists[migratetype];
- if (list_empty(list)) {
- pcp->count += rmqueue_bulk(zone, 0,
- pcp->batch, list,
- migratetype, cold);
- if (unlikely(list_empty(list)))
- goto failed;
- }
-
- if (cold)
- page = list_last_entry(list, struct page, lru);
- else
- page = list_first_entry(list, struct page, lru);
- list_del(&page->lru);
- pcp->count--;
+ if (likely(order == 0))
+ return rmqueue_pcplist(preferred_zone, zone, order,
+ gfp_flags, migratetype);
- } while (check_new_pcp(page));
- } else {
- /*
- * We most definitely don't want callers attempting to
- * allocate greater than order-1 page units with __GFP_NOFAIL.
- */
- WARN_ON_ONCE((gfp_flags & __GFP_NOFAIL) && (order > 1));
- spin_lock_irqsave(&zone->lock, flags);
+ /*
+ * We most definitely don't want callers attempting to
+ * allocate greater than order-1 page units with __GFP_NOFAIL.
+ */
+ WARN_ON_ONCE((gfp_flags & __GFP_NOFAIL) && (order > 1));
+ spin_lock_irqsave(&zone->lock, flags);
- do {
- page = NULL;
- if (alloc_flags & ALLOC_HARDER) {
- page = __rmqueue_smallest(zone, order, MIGRATE_HIGHATOMIC);
- if (page)
- trace_mm_page_alloc_zone_locked(page, order, migratetype);
- }
- if (!page)
- page = __rmqueue(zone, order, migratetype);
- } while (page && check_new_pages(page, order));
- spin_unlock(&zone->lock);
+ do {
+ page = NULL;
+ if (alloc_flags & ALLOC_HARDER) {
+ page = __rmqueue_smallest(zone, order, MIGRATE_HIGHATOMIC);
+ if (page)
+ trace_mm_page_alloc_zone_locked(page, order, migratetype);
+ }
if (!page)
- goto failed;
- __mod_zone_freepage_state(zone, -(1 << order),
- get_pcppage_migratetype(page));
- }
+ page = __rmqueue(zone, order, migratetype);
+ } while (page && check_new_pages(page, order));
+ spin_unlock(&zone->lock);
+ if (!page)
+ goto failed;
+ __mod_zone_freepage_state(zone, -(1 << order),
+ get_pcppage_migratetype(page));
__count_zid_vm_events(PGALLOC, page_zonenum(page), 1 << order);
zone_statistics(preferred_zone, zone, gfp_flags);
@@ -2982,7 +3010,7 @@ get_page_from_freelist(gfp_t gfp_mask, unsigned int order, int alloc_flags,
}
try_this_zone:
- page = buffered_rmqueue(ac->preferred_zoneref->zone, zone, order,
+ page = rmqueue(ac->preferred_zoneref->zone, zone, order,
gfp_mask, alloc_flags, ac->migratetype);
if (page) {
prep_new_page(page, order, gfp_mask, alloc_flags);
--
2.11.0
--
To unsubscribe, send a message with 'unsubscribe linux-mm' in
the body to majordomo@kvack.org. For more info on Linux MM,
see: http://www.linux-mm.org/ .
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^ permalink raw reply related [flat|nested] 26+ messages in thread
* [PATCH 2/4] mm, page_alloc: Split alloc_pages_nodemask
2017-01-04 11:10 ` Mel Gorman
@ 2017-01-04 11:10 ` Mel Gorman
-1 siblings, 0 replies; 26+ messages in thread
From: Mel Gorman @ 2017-01-04 11:10 UTC (permalink / raw)
To: Jesper Dangaard Brouer; +Cc: Linux Kernel, Linux-MM, Mel Gorman
alloc_pages_nodemask does a number of preperation steps that determine
what zones can be used for the allocation depending on a variety of
factors. This is fine but a hypothetical caller that wanted multiple
order-0 pages has to do the preparation steps multiple times. This patch
structures __alloc_pages_nodemask such that it's relatively easy to build
a bulk order-0 page allocator. There is no functional change.
Signed-off-by: Mel Gorman <mgorman@techsingularity.net>
---
mm/page_alloc.c | 81 ++++++++++++++++++++++++++++++++++-----------------------
1 file changed, 49 insertions(+), 32 deletions(-)
diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index d8798583eaf8..4a602b7f258d 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -3762,64 +3762,81 @@ __alloc_pages_slowpath(gfp_t gfp_mask, unsigned int order,
return page;
}
-/*
- * This is the 'heart' of the zoned buddy allocator.
- */
-struct page *
-__alloc_pages_nodemask(gfp_t gfp_mask, unsigned int order,
- struct zonelist *zonelist, nodemask_t *nodemask)
+static inline bool prepare_alloc_pages(gfp_t gfp_mask, unsigned int order,
+ struct zonelist *zonelist, nodemask_t *nodemask,
+ struct alloc_context *ac, gfp_t *alloc_mask,
+ unsigned int *alloc_flags)
{
- struct page *page;
- unsigned int cpuset_mems_cookie;
- unsigned int alloc_flags = ALLOC_WMARK_LOW;
- gfp_t alloc_mask = gfp_mask; /* The gfp_t that was actually used for allocation */
- struct alloc_context ac = {
- .high_zoneidx = gfp_zone(gfp_mask),
- .zonelist = zonelist,
- .nodemask = nodemask,
- .migratetype = gfpflags_to_migratetype(gfp_mask),
- };
+ ac->high_zoneidx = gfp_zone(gfp_mask);
+ ac->zonelist = zonelist;
+ ac->nodemask = nodemask;
+ ac->migratetype = gfpflags_to_migratetype(gfp_mask);
if (cpusets_enabled()) {
- alloc_mask |= __GFP_HARDWALL;
- alloc_flags |= ALLOC_CPUSET;
- if (!ac.nodemask)
- ac.nodemask = &cpuset_current_mems_allowed;
+ *alloc_mask |= __GFP_HARDWALL;
+ *alloc_flags |= ALLOC_CPUSET;
+ if (!ac->nodemask)
+ ac->nodemask = &cpuset_current_mems_allowed;
}
- gfp_mask &= gfp_allowed_mask;
-
lockdep_trace_alloc(gfp_mask);
might_sleep_if(gfp_mask & __GFP_DIRECT_RECLAIM);
if (should_fail_alloc_page(gfp_mask, order))
- return NULL;
+ return false;
/*
* Check the zones suitable for the gfp_mask contain at least one
* valid zone. It's possible to have an empty zonelist as a result
* of __GFP_THISNODE and a memoryless node
*/
- if (unlikely(!zonelist->_zonerefs->zone))
- return NULL;
+ if (unlikely(!ac->zonelist->_zonerefs->zone))
+ return false;
- if (IS_ENABLED(CONFIG_CMA) && ac.migratetype == MIGRATE_MOVABLE)
- alloc_flags |= ALLOC_CMA;
+ if (IS_ENABLED(CONFIG_CMA) && ac->migratetype == MIGRATE_MOVABLE)
+ *alloc_flags |= ALLOC_CMA;
-retry_cpuset:
- cpuset_mems_cookie = read_mems_allowed_begin();
+ return true;
+}
+/* Determine whether to spread dirty pages and what the first usable zone */
+static inline void finalise_ac(gfp_t gfp_mask,
+ unsigned int order, struct alloc_context *ac)
+{
/* Dirty zone balancing only done in the fast path */
- ac.spread_dirty_pages = (gfp_mask & __GFP_WRITE);
+ ac->spread_dirty_pages = (gfp_mask & __GFP_WRITE);
/*
* The preferred zone is used for statistics but crucially it is
* also used as the starting point for the zonelist iterator. It
* may get reset for allocations that ignore memory policies.
*/
- ac.preferred_zoneref = first_zones_zonelist(ac.zonelist,
- ac.high_zoneidx, ac.nodemask);
+ ac->preferred_zoneref = first_zones_zonelist(ac->zonelist,
+ ac->high_zoneidx, ac->nodemask);
+}
+
+/*
+ * This is the 'heart' of the zoned buddy allocator.
+ */
+struct page *
+__alloc_pages_nodemask(gfp_t gfp_mask, unsigned int order,
+ struct zonelist *zonelist, nodemask_t *nodemask)
+{
+ struct page *page;
+ unsigned int cpuset_mems_cookie;
+ unsigned int alloc_flags = ALLOC_WMARK_LOW;
+ gfp_t alloc_mask = gfp_mask; /* The gfp_t that was actually used for allocation */
+ struct alloc_context ac = { };
+
+ gfp_mask &= gfp_allowed_mask;
+ if (!prepare_alloc_pages(gfp_mask, order, zonelist, nodemask, &ac, &alloc_mask, &alloc_flags))
+ return NULL;
+
+retry_cpuset:
+ cpuset_mems_cookie = read_mems_allowed_begin();
+
+ finalise_ac(gfp_mask, order, &ac);
if (!ac.preferred_zoneref) {
page = NULL;
goto no_zone;
--
2.11.0
^ permalink raw reply related [flat|nested] 26+ messages in thread* [PATCH 2/4] mm, page_alloc: Split alloc_pages_nodemask
@ 2017-01-04 11:10 ` Mel Gorman
0 siblings, 0 replies; 26+ messages in thread
From: Mel Gorman @ 2017-01-04 11:10 UTC (permalink / raw)
To: Jesper Dangaard Brouer; +Cc: Linux Kernel, Linux-MM, Mel Gorman
alloc_pages_nodemask does a number of preperation steps that determine
what zones can be used for the allocation depending on a variety of
factors. This is fine but a hypothetical caller that wanted multiple
order-0 pages has to do the preparation steps multiple times. This patch
structures __alloc_pages_nodemask such that it's relatively easy to build
a bulk order-0 page allocator. There is no functional change.
Signed-off-by: Mel Gorman <mgorman@techsingularity.net>
---
mm/page_alloc.c | 81 ++++++++++++++++++++++++++++++++++-----------------------
1 file changed, 49 insertions(+), 32 deletions(-)
diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index d8798583eaf8..4a602b7f258d 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -3762,64 +3762,81 @@ __alloc_pages_slowpath(gfp_t gfp_mask, unsigned int order,
return page;
}
-/*
- * This is the 'heart' of the zoned buddy allocator.
- */
-struct page *
-__alloc_pages_nodemask(gfp_t gfp_mask, unsigned int order,
- struct zonelist *zonelist, nodemask_t *nodemask)
+static inline bool prepare_alloc_pages(gfp_t gfp_mask, unsigned int order,
+ struct zonelist *zonelist, nodemask_t *nodemask,
+ struct alloc_context *ac, gfp_t *alloc_mask,
+ unsigned int *alloc_flags)
{
- struct page *page;
- unsigned int cpuset_mems_cookie;
- unsigned int alloc_flags = ALLOC_WMARK_LOW;
- gfp_t alloc_mask = gfp_mask; /* The gfp_t that was actually used for allocation */
- struct alloc_context ac = {
- .high_zoneidx = gfp_zone(gfp_mask),
- .zonelist = zonelist,
- .nodemask = nodemask,
- .migratetype = gfpflags_to_migratetype(gfp_mask),
- };
+ ac->high_zoneidx = gfp_zone(gfp_mask);
+ ac->zonelist = zonelist;
+ ac->nodemask = nodemask;
+ ac->migratetype = gfpflags_to_migratetype(gfp_mask);
if (cpusets_enabled()) {
- alloc_mask |= __GFP_HARDWALL;
- alloc_flags |= ALLOC_CPUSET;
- if (!ac.nodemask)
- ac.nodemask = &cpuset_current_mems_allowed;
+ *alloc_mask |= __GFP_HARDWALL;
+ *alloc_flags |= ALLOC_CPUSET;
+ if (!ac->nodemask)
+ ac->nodemask = &cpuset_current_mems_allowed;
}
- gfp_mask &= gfp_allowed_mask;
-
lockdep_trace_alloc(gfp_mask);
might_sleep_if(gfp_mask & __GFP_DIRECT_RECLAIM);
if (should_fail_alloc_page(gfp_mask, order))
- return NULL;
+ return false;
/*
* Check the zones suitable for the gfp_mask contain at least one
* valid zone. It's possible to have an empty zonelist as a result
* of __GFP_THISNODE and a memoryless node
*/
- if (unlikely(!zonelist->_zonerefs->zone))
- return NULL;
+ if (unlikely(!ac->zonelist->_zonerefs->zone))
+ return false;
- if (IS_ENABLED(CONFIG_CMA) && ac.migratetype == MIGRATE_MOVABLE)
- alloc_flags |= ALLOC_CMA;
+ if (IS_ENABLED(CONFIG_CMA) && ac->migratetype == MIGRATE_MOVABLE)
+ *alloc_flags |= ALLOC_CMA;
-retry_cpuset:
- cpuset_mems_cookie = read_mems_allowed_begin();
+ return true;
+}
+/* Determine whether to spread dirty pages and what the first usable zone */
+static inline void finalise_ac(gfp_t gfp_mask,
+ unsigned int order, struct alloc_context *ac)
+{
/* Dirty zone balancing only done in the fast path */
- ac.spread_dirty_pages = (gfp_mask & __GFP_WRITE);
+ ac->spread_dirty_pages = (gfp_mask & __GFP_WRITE);
/*
* The preferred zone is used for statistics but crucially it is
* also used as the starting point for the zonelist iterator. It
* may get reset for allocations that ignore memory policies.
*/
- ac.preferred_zoneref = first_zones_zonelist(ac.zonelist,
- ac.high_zoneidx, ac.nodemask);
+ ac->preferred_zoneref = first_zones_zonelist(ac->zonelist,
+ ac->high_zoneidx, ac->nodemask);
+}
+
+/*
+ * This is the 'heart' of the zoned buddy allocator.
+ */
+struct page *
+__alloc_pages_nodemask(gfp_t gfp_mask, unsigned int order,
+ struct zonelist *zonelist, nodemask_t *nodemask)
+{
+ struct page *page;
+ unsigned int cpuset_mems_cookie;
+ unsigned int alloc_flags = ALLOC_WMARK_LOW;
+ gfp_t alloc_mask = gfp_mask; /* The gfp_t that was actually used for allocation */
+ struct alloc_context ac = { };
+
+ gfp_mask &= gfp_allowed_mask;
+ if (!prepare_alloc_pages(gfp_mask, order, zonelist, nodemask, &ac, &alloc_mask, &alloc_flags))
+ return NULL;
+
+retry_cpuset:
+ cpuset_mems_cookie = read_mems_allowed_begin();
+
+ finalise_ac(gfp_mask, order, &ac);
if (!ac.preferred_zoneref) {
page = NULL;
goto no_zone;
--
2.11.0
--
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^ permalink raw reply related [flat|nested] 26+ messages in thread
* [PATCH 3/4] mm, page_allocator: Only use per-cpu allocator for irq-safe requests
2017-01-04 11:10 ` Mel Gorman
@ 2017-01-04 11:10 ` Mel Gorman
-1 siblings, 0 replies; 26+ messages in thread
From: Mel Gorman @ 2017-01-04 11:10 UTC (permalink / raw)
To: Jesper Dangaard Brouer; +Cc: Linux Kernel, Linux-MM, Mel Gorman
Many workloads that allocate pages are not handling an interrupt at a
time. As allocation requests may be from IRQ context, it's necessary to
disable/enable IRQs for every page allocation. This cost is the bulk
of the free path but also a significant percentage of the allocation
path.
This patch alters the locking and checks such that only irq-safe allocation
requests use the per-cpu allocator. All others acquire the irq-safe
zone->lock and allocate from the buddy allocator. It relies on disabling
preemption to safely access the per-cpu structures. It could be slightly
modified to avoid soft IRQs using it but it's not clear it's worthwhile.
This modification may slow allocations from IRQ context slightly but the main
gain from the per-cpu allocator is that it scales better for allocations
from multiple contexts. There is an implicit assumption that intensive
allocations from IRQ contexts on multiple CPUs from a single NUMA node are
rare and that the fast majority of scaling issues are encountered in !IRQ
contexts such as page faulting. It's worth noting that this patch is not
required for a bulk page allocator but it significantly reduces the overhead.
The following is results from a page allocator micro-benchmark. Only
order-0 is interesting as higher orders do not use the per-cpu allocator
4.10.0-rc2 4.10.0-rc2
vanilla irqsafe-v1r5
Amean alloc-odr0-1 287.15 ( 0.00%) 219.00 ( 23.73%)
Amean alloc-odr0-2 221.23 ( 0.00%) 183.23 ( 17.18%)
Amean alloc-odr0-4 187.00 ( 0.00%) 151.38 ( 19.05%)
Amean alloc-odr0-8 167.54 ( 0.00%) 132.77 ( 20.75%)
Amean alloc-odr0-16 156.00 ( 0.00%) 123.00 ( 21.15%)
Amean alloc-odr0-32 149.00 ( 0.00%) 118.31 ( 20.60%)
Amean alloc-odr0-64 138.77 ( 0.00%) 116.00 ( 16.41%)
Amean alloc-odr0-128 145.00 ( 0.00%) 118.00 ( 18.62%)
Amean alloc-odr0-256 136.15 ( 0.00%) 125.00 ( 8.19%)
Amean alloc-odr0-512 147.92 ( 0.00%) 121.77 ( 17.68%)
Amean alloc-odr0-1024 147.23 ( 0.00%) 126.15 ( 14.32%)
Amean alloc-odr0-2048 155.15 ( 0.00%) 129.92 ( 16.26%)
Amean alloc-odr0-4096 164.00 ( 0.00%) 136.77 ( 16.60%)
Amean alloc-odr0-8192 166.92 ( 0.00%) 138.08 ( 17.28%)
Amean alloc-odr0-16384 159.00 ( 0.00%) 138.00 ( 13.21%)
Amean free-odr0-1 165.00 ( 0.00%) 89.00 ( 46.06%)
Amean free-odr0-2 113.00 ( 0.00%) 63.00 ( 44.25%)
Amean free-odr0-4 99.00 ( 0.00%) 54.00 ( 45.45%)
Amean free-odr0-8 88.00 ( 0.00%) 47.38 ( 46.15%)
Amean free-odr0-16 83.00 ( 0.00%) 46.00 ( 44.58%)
Amean free-odr0-32 80.00 ( 0.00%) 44.38 ( 44.52%)
Amean free-odr0-64 72.62 ( 0.00%) 43.00 ( 40.78%)
Amean free-odr0-128 78.00 ( 0.00%) 42.00 ( 46.15%)
Amean free-odr0-256 80.46 ( 0.00%) 57.00 ( 29.16%)
Amean free-odr0-512 96.38 ( 0.00%) 64.69 ( 32.88%)
Amean free-odr0-1024 107.31 ( 0.00%) 72.54 ( 32.40%)
Amean free-odr0-2048 108.92 ( 0.00%) 78.08 ( 28.32%)
Amean free-odr0-4096 113.38 ( 0.00%) 82.23 ( 27.48%)
Amean free-odr0-8192 112.08 ( 0.00%) 82.85 ( 26.08%)
Amean free-odr0-16384 110.38 ( 0.00%) 81.92 ( 25.78%)
Amean total-odr0-1 452.15 ( 0.00%) 308.00 ( 31.88%)
Amean total-odr0-2 334.23 ( 0.00%) 246.23 ( 26.33%)
Amean total-odr0-4 286.00 ( 0.00%) 205.38 ( 28.19%)
Amean total-odr0-8 255.54 ( 0.00%) 180.15 ( 29.50%)
Amean total-odr0-16 239.00 ( 0.00%) 169.00 ( 29.29%)
Amean total-odr0-32 229.00 ( 0.00%) 162.69 ( 28.96%)
Amean total-odr0-64 211.38 ( 0.00%) 159.00 ( 24.78%)
Amean total-odr0-128 223.00 ( 0.00%) 160.00 ( 28.25%)
Amean total-odr0-256 216.62 ( 0.00%) 182.00 ( 15.98%)
Amean total-odr0-512 244.31 ( 0.00%) 186.46 ( 23.68%)
Amean total-odr0-1024 254.54 ( 0.00%) 198.69 ( 21.94%)
Amean total-odr0-2048 264.08 ( 0.00%) 208.00 ( 21.24%)
Amean total-odr0-4096 277.38 ( 0.00%) 219.00 ( 21.05%)
Amean total-odr0-8192 279.00 ( 0.00%) 220.92 ( 20.82%)
Amean total-odr0-16384 269.38 ( 0.00%) 219.92 ( 18.36%)
This is the alloc, free and total overhead of allocating order-0 pages in
batches of 1 page up to 16384 pages. Avoiding disabling/enabling overhead
massively reduces overhead. Alloc overhead is roughly reduced by 14-20% in
most cases. The free path is reduced by 26-46% and the total reduction
is significant.
Many users require zeroing of pages from the page allocator which is the
vast cost of allocation. Hence, the impact on a basic page faulting benchmark
is not that significant
4.10.0-rc2 4.10.0-rc2
vanilla irqsafe-v1r5
Hmean page_test 656632.98 ( 0.00%) 675536.13 ( 2.88%)
Hmean brk_test 3845502.67 ( 0.00%) 3867186.94 ( 0.56%)
Stddev page_test 10543.29 ( 0.00%) 4104.07 ( 61.07%)
Stddev brk_test 33472.36 ( 0.00%) 15538.39 ( 53.58%)
CoeffVar page_test 1.61 ( 0.00%) 0.61 ( 62.15%)
CoeffVar brk_test 0.87 ( 0.00%) 0.40 ( 53.84%)
Max page_test 666513.33 ( 0.00%) 678640.00 ( 1.82%)
Max brk_test 3882800.00 ( 0.00%) 3887008.66 ( 0.11%)
This is from aim9 and the most notable outcome is that fault variability
is reduced by the patch. The headline improvement is small as the overall
fault cost, zeroing, page table insertion etc dominate relative to
disabling/enabling IRQs in the per-cpu allocator.
Similarly, little benefit was seen on networking benchmarks both localhost
and between physical server/clients where other costs dominate. It's
possible that this will only be noticable on very high speed networks.
Signed-off-by: Mel Gorman <mgorman@techsingularity.net>
---
mm/page_alloc.c | 38 +++++++++++++++++---------------------
1 file changed, 17 insertions(+), 21 deletions(-)
diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index 4a602b7f258d..01b09f9da288 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -1087,10 +1087,10 @@ static void free_pcppages_bulk(struct zone *zone, int count,
{
int migratetype = 0;
int batch_free = 0;
- unsigned long nr_scanned;
+ unsigned long nr_scanned, flags;
bool isolated_pageblocks;
- spin_lock(&zone->lock);
+ spin_lock_irqsave(&zone->lock, flags);
isolated_pageblocks = has_isolate_pageblock(zone);
nr_scanned = node_page_state(zone->zone_pgdat, NR_PAGES_SCANNED);
if (nr_scanned)
@@ -1139,7 +1139,7 @@ static void free_pcppages_bulk(struct zone *zone, int count,
trace_mm_page_pcpu_drain(page, 0, mt);
} while (--count && --batch_free && !list_empty(list));
}
- spin_unlock(&zone->lock);
+ spin_unlock_irqrestore(&zone->lock, flags);
}
static void free_one_page(struct zone *zone,
@@ -1147,8 +1147,8 @@ static void free_one_page(struct zone *zone,
unsigned int order,
int migratetype)
{
- unsigned long nr_scanned;
- spin_lock(&zone->lock);
+ unsigned long nr_scanned, flags;
+ spin_lock_irqsave(&zone->lock, flags);
nr_scanned = node_page_state(zone->zone_pgdat, NR_PAGES_SCANNED);
if (nr_scanned)
__mod_node_page_state(zone->zone_pgdat, NR_PAGES_SCANNED, -nr_scanned);
@@ -1158,7 +1158,7 @@ static void free_one_page(struct zone *zone,
migratetype = get_pfnblock_migratetype(page, pfn);
}
__free_one_page(page, pfn, zone, order, migratetype);
- spin_unlock(&zone->lock);
+ spin_unlock_irqrestore(&zone->lock, flags);
}
static void __meminit __init_single_page(struct page *page, unsigned long pfn,
@@ -1236,7 +1236,6 @@ void __meminit reserve_bootmem_region(phys_addr_t start, phys_addr_t end)
static void __free_pages_ok(struct page *page, unsigned int order)
{
- unsigned long flags;
int migratetype;
unsigned long pfn = page_to_pfn(page);
@@ -1244,10 +1243,8 @@ static void __free_pages_ok(struct page *page, unsigned int order)
return;
migratetype = get_pfnblock_migratetype(page, pfn);
- local_irq_save(flags);
- __count_vm_events(PGFREE, 1 << order);
+ count_vm_events(PGFREE, 1 << order);
free_one_page(page_zone(page), page, pfn, order, migratetype);
- local_irq_restore(flags);
}
static void __init __free_pages_boot_core(struct page *page, unsigned int order)
@@ -2219,8 +2216,9 @@ static int rmqueue_bulk(struct zone *zone, unsigned int order,
int migratetype, bool cold)
{
int i, alloced = 0;
+ unsigned long flags;
- spin_lock(&zone->lock);
+ spin_lock_irqsave(&zone->lock, flags);
for (i = 0; i < count; ++i) {
struct page *page = __rmqueue(zone, order, migratetype);
if (unlikely(page == NULL))
@@ -2256,7 +2254,7 @@ static int rmqueue_bulk(struct zone *zone, unsigned int order,
* pages added to the pcp list.
*/
__mod_zone_page_state(zone, NR_FREE_PAGES, -(i << order));
- spin_unlock(&zone->lock);
+ spin_unlock_irqrestore(&zone->lock, flags);
return alloced;
}
@@ -2444,7 +2442,6 @@ void free_hot_cold_page(struct page *page, bool cold)
{
struct zone *zone = page_zone(page);
struct per_cpu_pages *pcp;
- unsigned long flags;
unsigned long pfn = page_to_pfn(page);
int migratetype;
@@ -2453,8 +2450,8 @@ void free_hot_cold_page(struct page *page, bool cold)
migratetype = get_pfnblock_migratetype(page, pfn);
set_pcppage_migratetype(page, migratetype);
- local_irq_save(flags);
- __count_vm_event(PGFREE);
+ preempt_disable();
+ count_vm_event(PGFREE);
/*
* We only track unmovable, reclaimable and movable on pcp lists.
@@ -2484,7 +2481,7 @@ void free_hot_cold_page(struct page *page, bool cold)
}
out:
- local_irq_restore(flags);
+ preempt_enable();
}
/*
@@ -2647,9 +2644,8 @@ static struct page *rmqueue_pcplist(struct zone *preferred_zone,
struct list_head *list;
bool cold = ((gfp_flags & __GFP_COLD) != 0);
struct page *page;
- unsigned long flags;
- local_irq_save(flags);
+ preempt_disable();
pcp = &this_cpu_ptr(zone->pageset)->pcp;
list = &pcp->lists[migratetype];
page = __rmqueue_pcplist(zone, order, gfp_flags, migratetype,
@@ -2658,7 +2654,7 @@ static struct page *rmqueue_pcplist(struct zone *preferred_zone,
__count_zid_vm_events(PGALLOC, page_zonenum(page), 1 << order);
zone_statistics(preferred_zone, zone, gfp_flags);
}
- local_irq_restore(flags);
+ preempt_enable();
return page;
}
@@ -2674,7 +2670,7 @@ struct page *rmqueue(struct zone *preferred_zone,
unsigned long flags;
struct page *page;
- if (likely(order == 0))
+ if (likely(order == 0) && !in_interrupt())
return rmqueue_pcplist(preferred_zone, zone, order,
gfp_flags, migratetype);
@@ -3919,7 +3915,7 @@ EXPORT_SYMBOL(get_zeroed_page);
void __free_pages(struct page *page, unsigned int order)
{
if (put_page_testzero(page)) {
- if (order == 0)
+ if (order == 0 && !in_interrupt())
free_hot_cold_page(page, false);
else
__free_pages_ok(page, order);
--
2.11.0
^ permalink raw reply related [flat|nested] 26+ messages in thread* [PATCH 3/4] mm, page_allocator: Only use per-cpu allocator for irq-safe requests
@ 2017-01-04 11:10 ` Mel Gorman
0 siblings, 0 replies; 26+ messages in thread
From: Mel Gorman @ 2017-01-04 11:10 UTC (permalink / raw)
To: Jesper Dangaard Brouer; +Cc: Linux Kernel, Linux-MM, Mel Gorman
Many workloads that allocate pages are not handling an interrupt at a
time. As allocation requests may be from IRQ context, it's necessary to
disable/enable IRQs for every page allocation. This cost is the bulk
of the free path but also a significant percentage of the allocation
path.
This patch alters the locking and checks such that only irq-safe allocation
requests use the per-cpu allocator. All others acquire the irq-safe
zone->lock and allocate from the buddy allocator. It relies on disabling
preemption to safely access the per-cpu structures. It could be slightly
modified to avoid soft IRQs using it but it's not clear it's worthwhile.
This modification may slow allocations from IRQ context slightly but the main
gain from the per-cpu allocator is that it scales better for allocations
from multiple contexts. There is an implicit assumption that intensive
allocations from IRQ contexts on multiple CPUs from a single NUMA node are
rare and that the fast majority of scaling issues are encountered in !IRQ
contexts such as page faulting. It's worth noting that this patch is not
required for a bulk page allocator but it significantly reduces the overhead.
The following is results from a page allocator micro-benchmark. Only
order-0 is interesting as higher orders do not use the per-cpu allocator
4.10.0-rc2 4.10.0-rc2
vanilla irqsafe-v1r5
Amean alloc-odr0-1 287.15 ( 0.00%) 219.00 ( 23.73%)
Amean alloc-odr0-2 221.23 ( 0.00%) 183.23 ( 17.18%)
Amean alloc-odr0-4 187.00 ( 0.00%) 151.38 ( 19.05%)
Amean alloc-odr0-8 167.54 ( 0.00%) 132.77 ( 20.75%)
Amean alloc-odr0-16 156.00 ( 0.00%) 123.00 ( 21.15%)
Amean alloc-odr0-32 149.00 ( 0.00%) 118.31 ( 20.60%)
Amean alloc-odr0-64 138.77 ( 0.00%) 116.00 ( 16.41%)
Amean alloc-odr0-128 145.00 ( 0.00%) 118.00 ( 18.62%)
Amean alloc-odr0-256 136.15 ( 0.00%) 125.00 ( 8.19%)
Amean alloc-odr0-512 147.92 ( 0.00%) 121.77 ( 17.68%)
Amean alloc-odr0-1024 147.23 ( 0.00%) 126.15 ( 14.32%)
Amean alloc-odr0-2048 155.15 ( 0.00%) 129.92 ( 16.26%)
Amean alloc-odr0-4096 164.00 ( 0.00%) 136.77 ( 16.60%)
Amean alloc-odr0-8192 166.92 ( 0.00%) 138.08 ( 17.28%)
Amean alloc-odr0-16384 159.00 ( 0.00%) 138.00 ( 13.21%)
Amean free-odr0-1 165.00 ( 0.00%) 89.00 ( 46.06%)
Amean free-odr0-2 113.00 ( 0.00%) 63.00 ( 44.25%)
Amean free-odr0-4 99.00 ( 0.00%) 54.00 ( 45.45%)
Amean free-odr0-8 88.00 ( 0.00%) 47.38 ( 46.15%)
Amean free-odr0-16 83.00 ( 0.00%) 46.00 ( 44.58%)
Amean free-odr0-32 80.00 ( 0.00%) 44.38 ( 44.52%)
Amean free-odr0-64 72.62 ( 0.00%) 43.00 ( 40.78%)
Amean free-odr0-128 78.00 ( 0.00%) 42.00 ( 46.15%)
Amean free-odr0-256 80.46 ( 0.00%) 57.00 ( 29.16%)
Amean free-odr0-512 96.38 ( 0.00%) 64.69 ( 32.88%)
Amean free-odr0-1024 107.31 ( 0.00%) 72.54 ( 32.40%)
Amean free-odr0-2048 108.92 ( 0.00%) 78.08 ( 28.32%)
Amean free-odr0-4096 113.38 ( 0.00%) 82.23 ( 27.48%)
Amean free-odr0-8192 112.08 ( 0.00%) 82.85 ( 26.08%)
Amean free-odr0-16384 110.38 ( 0.00%) 81.92 ( 25.78%)
Amean total-odr0-1 452.15 ( 0.00%) 308.00 ( 31.88%)
Amean total-odr0-2 334.23 ( 0.00%) 246.23 ( 26.33%)
Amean total-odr0-4 286.00 ( 0.00%) 205.38 ( 28.19%)
Amean total-odr0-8 255.54 ( 0.00%) 180.15 ( 29.50%)
Amean total-odr0-16 239.00 ( 0.00%) 169.00 ( 29.29%)
Amean total-odr0-32 229.00 ( 0.00%) 162.69 ( 28.96%)
Amean total-odr0-64 211.38 ( 0.00%) 159.00 ( 24.78%)
Amean total-odr0-128 223.00 ( 0.00%) 160.00 ( 28.25%)
Amean total-odr0-256 216.62 ( 0.00%) 182.00 ( 15.98%)
Amean total-odr0-512 244.31 ( 0.00%) 186.46 ( 23.68%)
Amean total-odr0-1024 254.54 ( 0.00%) 198.69 ( 21.94%)
Amean total-odr0-2048 264.08 ( 0.00%) 208.00 ( 21.24%)
Amean total-odr0-4096 277.38 ( 0.00%) 219.00 ( 21.05%)
Amean total-odr0-8192 279.00 ( 0.00%) 220.92 ( 20.82%)
Amean total-odr0-16384 269.38 ( 0.00%) 219.92 ( 18.36%)
This is the alloc, free and total overhead of allocating order-0 pages in
batches of 1 page up to 16384 pages. Avoiding disabling/enabling overhead
massively reduces overhead. Alloc overhead is roughly reduced by 14-20% in
most cases. The free path is reduced by 26-46% and the total reduction
is significant.
Many users require zeroing of pages from the page allocator which is the
vast cost of allocation. Hence, the impact on a basic page faulting benchmark
is not that significant
4.10.0-rc2 4.10.0-rc2
vanilla irqsafe-v1r5
Hmean page_test 656632.98 ( 0.00%) 675536.13 ( 2.88%)
Hmean brk_test 3845502.67 ( 0.00%) 3867186.94 ( 0.56%)
Stddev page_test 10543.29 ( 0.00%) 4104.07 ( 61.07%)
Stddev brk_test 33472.36 ( 0.00%) 15538.39 ( 53.58%)
CoeffVar page_test 1.61 ( 0.00%) 0.61 ( 62.15%)
CoeffVar brk_test 0.87 ( 0.00%) 0.40 ( 53.84%)
Max page_test 666513.33 ( 0.00%) 678640.00 ( 1.82%)
Max brk_test 3882800.00 ( 0.00%) 3887008.66 ( 0.11%)
This is from aim9 and the most notable outcome is that fault variability
is reduced by the patch. The headline improvement is small as the overall
fault cost, zeroing, page table insertion etc dominate relative to
disabling/enabling IRQs in the per-cpu allocator.
Similarly, little benefit was seen on networking benchmarks both localhost
and between physical server/clients where other costs dominate. It's
possible that this will only be noticable on very high speed networks.
Signed-off-by: Mel Gorman <mgorman@techsingularity.net>
---
mm/page_alloc.c | 38 +++++++++++++++++---------------------
1 file changed, 17 insertions(+), 21 deletions(-)
diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index 4a602b7f258d..01b09f9da288 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -1087,10 +1087,10 @@ static void free_pcppages_bulk(struct zone *zone, int count,
{
int migratetype = 0;
int batch_free = 0;
- unsigned long nr_scanned;
+ unsigned long nr_scanned, flags;
bool isolated_pageblocks;
- spin_lock(&zone->lock);
+ spin_lock_irqsave(&zone->lock, flags);
isolated_pageblocks = has_isolate_pageblock(zone);
nr_scanned = node_page_state(zone->zone_pgdat, NR_PAGES_SCANNED);
if (nr_scanned)
@@ -1139,7 +1139,7 @@ static void free_pcppages_bulk(struct zone *zone, int count,
trace_mm_page_pcpu_drain(page, 0, mt);
} while (--count && --batch_free && !list_empty(list));
}
- spin_unlock(&zone->lock);
+ spin_unlock_irqrestore(&zone->lock, flags);
}
static void free_one_page(struct zone *zone,
@@ -1147,8 +1147,8 @@ static void free_one_page(struct zone *zone,
unsigned int order,
int migratetype)
{
- unsigned long nr_scanned;
- spin_lock(&zone->lock);
+ unsigned long nr_scanned, flags;
+ spin_lock_irqsave(&zone->lock, flags);
nr_scanned = node_page_state(zone->zone_pgdat, NR_PAGES_SCANNED);
if (nr_scanned)
__mod_node_page_state(zone->zone_pgdat, NR_PAGES_SCANNED, -nr_scanned);
@@ -1158,7 +1158,7 @@ static void free_one_page(struct zone *zone,
migratetype = get_pfnblock_migratetype(page, pfn);
}
__free_one_page(page, pfn, zone, order, migratetype);
- spin_unlock(&zone->lock);
+ spin_unlock_irqrestore(&zone->lock, flags);
}
static void __meminit __init_single_page(struct page *page, unsigned long pfn,
@@ -1236,7 +1236,6 @@ void __meminit reserve_bootmem_region(phys_addr_t start, phys_addr_t end)
static void __free_pages_ok(struct page *page, unsigned int order)
{
- unsigned long flags;
int migratetype;
unsigned long pfn = page_to_pfn(page);
@@ -1244,10 +1243,8 @@ static void __free_pages_ok(struct page *page, unsigned int order)
return;
migratetype = get_pfnblock_migratetype(page, pfn);
- local_irq_save(flags);
- __count_vm_events(PGFREE, 1 << order);
+ count_vm_events(PGFREE, 1 << order);
free_one_page(page_zone(page), page, pfn, order, migratetype);
- local_irq_restore(flags);
}
static void __init __free_pages_boot_core(struct page *page, unsigned int order)
@@ -2219,8 +2216,9 @@ static int rmqueue_bulk(struct zone *zone, unsigned int order,
int migratetype, bool cold)
{
int i, alloced = 0;
+ unsigned long flags;
- spin_lock(&zone->lock);
+ spin_lock_irqsave(&zone->lock, flags);
for (i = 0; i < count; ++i) {
struct page *page = __rmqueue(zone, order, migratetype);
if (unlikely(page == NULL))
@@ -2256,7 +2254,7 @@ static int rmqueue_bulk(struct zone *zone, unsigned int order,
* pages added to the pcp list.
*/
__mod_zone_page_state(zone, NR_FREE_PAGES, -(i << order));
- spin_unlock(&zone->lock);
+ spin_unlock_irqrestore(&zone->lock, flags);
return alloced;
}
@@ -2444,7 +2442,6 @@ void free_hot_cold_page(struct page *page, bool cold)
{
struct zone *zone = page_zone(page);
struct per_cpu_pages *pcp;
- unsigned long flags;
unsigned long pfn = page_to_pfn(page);
int migratetype;
@@ -2453,8 +2450,8 @@ void free_hot_cold_page(struct page *page, bool cold)
migratetype = get_pfnblock_migratetype(page, pfn);
set_pcppage_migratetype(page, migratetype);
- local_irq_save(flags);
- __count_vm_event(PGFREE);
+ preempt_disable();
+ count_vm_event(PGFREE);
/*
* We only track unmovable, reclaimable and movable on pcp lists.
@@ -2484,7 +2481,7 @@ void free_hot_cold_page(struct page *page, bool cold)
}
out:
- local_irq_restore(flags);
+ preempt_enable();
}
/*
@@ -2647,9 +2644,8 @@ static struct page *rmqueue_pcplist(struct zone *preferred_zone,
struct list_head *list;
bool cold = ((gfp_flags & __GFP_COLD) != 0);
struct page *page;
- unsigned long flags;
- local_irq_save(flags);
+ preempt_disable();
pcp = &this_cpu_ptr(zone->pageset)->pcp;
list = &pcp->lists[migratetype];
page = __rmqueue_pcplist(zone, order, gfp_flags, migratetype,
@@ -2658,7 +2654,7 @@ static struct page *rmqueue_pcplist(struct zone *preferred_zone,
__count_zid_vm_events(PGALLOC, page_zonenum(page), 1 << order);
zone_statistics(preferred_zone, zone, gfp_flags);
}
- local_irq_restore(flags);
+ preempt_enable();
return page;
}
@@ -2674,7 +2670,7 @@ struct page *rmqueue(struct zone *preferred_zone,
unsigned long flags;
struct page *page;
- if (likely(order == 0))
+ if (likely(order == 0) && !in_interrupt())
return rmqueue_pcplist(preferred_zone, zone, order,
gfp_flags, migratetype);
@@ -3919,7 +3915,7 @@ EXPORT_SYMBOL(get_zeroed_page);
void __free_pages(struct page *page, unsigned int order)
{
if (put_page_testzero(page)) {
- if (order == 0)
+ if (order == 0 && !in_interrupt())
free_hot_cold_page(page, false);
else
__free_pages_ok(page, order);
--
2.11.0
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^ permalink raw reply related [flat|nested] 26+ messages in thread* Re: [PATCH 3/4] mm, page_allocator: Only use per-cpu allocator for irq-safe requests
2017-01-04 11:10 ` Mel Gorman
@ 2017-01-04 14:20 ` Jesper Dangaard Brouer
-1 siblings, 0 replies; 26+ messages in thread
From: Jesper Dangaard Brouer @ 2017-01-04 14:20 UTC (permalink / raw)
To: Mel Gorman; +Cc: Linux Kernel, Linux-MM, brouer
On Wed, 4 Jan 2017 11:10:48 +0000 Mel Gorman <mgorman@techsingularity.net> wrote:
> Many workloads that allocate pages are not handling an interrupt at a
> time. As allocation requests may be from IRQ context, it's necessary to
> disable/enable IRQs for every page allocation. This cost is the bulk
> of the free path but also a significant percentage of the allocation
> path.
>
> This patch alters the locking and checks such that only irq-safe allocation
> requests use the per-cpu allocator. All others acquire the irq-safe
> zone->lock and allocate from the buddy allocator. It relies on disabling
> preemption to safely access the per-cpu structures.
I love this idea and patch :-)
> It could be slightly
> modified to avoid soft IRQs using it but it's not clear it's worthwhile.
NICs usually refill their RX-ring from SoftIRQ context (NAPI).
Thus, we do want this optimization to work in softirq.
> This modification may slow allocations from IRQ context slightly but the main
> gain from the per-cpu allocator is that it scales better for allocations
> from multiple contexts. There is an implicit assumption that intensive
> allocations from IRQ contexts on multiple CPUs from a single NUMA node are
> rare and that the fast majority of scaling issues are encountered in !IRQ
> contexts such as page faulting.
IHMO, I agree with this implicit assumption.
> It's worth noting that this patch is not
> required for a bulk page allocator but it significantly reduces the overhead.
>
> The following is results from a page allocator micro-benchmark. Only
> order-0 is interesting as higher orders do not use the per-cpu allocator
I'm seeing approx 34% reduction in a order-0 micro-benchmark! amazing! :-)
[1] https://github.com/netoptimizer/prototype-kernel/blob/master/kernel/mm/bench/
> 4.10.0-rc2 4.10.0-rc2
> vanilla irqsafe-v1r5
> Amean alloc-odr0-1 287.15 ( 0.00%) 219.00 ( 23.73%)
> Amean alloc-odr0-2 221.23 ( 0.00%) 183.23 ( 17.18%)
> Amean alloc-odr0-4 187.00 ( 0.00%) 151.38 ( 19.05%)
> Amean alloc-odr0-8 167.54 ( 0.00%) 132.77 ( 20.75%)
> Amean alloc-odr0-16 156.00 ( 0.00%) 123.00 ( 21.15%)
> Amean alloc-odr0-32 149.00 ( 0.00%) 118.31 ( 20.60%)
> Amean alloc-odr0-64 138.77 ( 0.00%) 116.00 ( 16.41%)
> Amean alloc-odr0-128 145.00 ( 0.00%) 118.00 ( 18.62%)
> Amean alloc-odr0-256 136.15 ( 0.00%) 125.00 ( 8.19%)
> Amean alloc-odr0-512 147.92 ( 0.00%) 121.77 ( 17.68%)
> Amean alloc-odr0-1024 147.23 ( 0.00%) 126.15 ( 14.32%)
> Amean alloc-odr0-2048 155.15 ( 0.00%) 129.92 ( 16.26%)
> Amean alloc-odr0-4096 164.00 ( 0.00%) 136.77 ( 16.60%)
> Amean alloc-odr0-8192 166.92 ( 0.00%) 138.08 ( 17.28%)
> Amean alloc-odr0-16384 159.00 ( 0.00%) 138.00 ( 13.21%)
> Amean free-odr0-1 165.00 ( 0.00%) 89.00 ( 46.06%)
> Amean free-odr0-2 113.00 ( 0.00%) 63.00 ( 44.25%)
> Amean free-odr0-4 99.00 ( 0.00%) 54.00 ( 45.45%)
> Amean free-odr0-8 88.00 ( 0.00%) 47.38 ( 46.15%)
> Amean free-odr0-16 83.00 ( 0.00%) 46.00 ( 44.58%)
> Amean free-odr0-32 80.00 ( 0.00%) 44.38 ( 44.52%)
> Amean free-odr0-64 72.62 ( 0.00%) 43.00 ( 40.78%)
> Amean free-odr0-128 78.00 ( 0.00%) 42.00 ( 46.15%)
> Amean free-odr0-256 80.46 ( 0.00%) 57.00 ( 29.16%)
> Amean free-odr0-512 96.38 ( 0.00%) 64.69 ( 32.88%)
> Amean free-odr0-1024 107.31 ( 0.00%) 72.54 ( 32.40%)
> Amean free-odr0-2048 108.92 ( 0.00%) 78.08 ( 28.32%)
> Amean free-odr0-4096 113.38 ( 0.00%) 82.23 ( 27.48%)
> Amean free-odr0-8192 112.08 ( 0.00%) 82.85 ( 26.08%)
> Amean free-odr0-16384 110.38 ( 0.00%) 81.92 ( 25.78%)
> Amean total-odr0-1 452.15 ( 0.00%) 308.00 ( 31.88%)
> Amean total-odr0-2 334.23 ( 0.00%) 246.23 ( 26.33%)
> Amean total-odr0-4 286.00 ( 0.00%) 205.38 ( 28.19%)
> Amean total-odr0-8 255.54 ( 0.00%) 180.15 ( 29.50%)
> Amean total-odr0-16 239.00 ( 0.00%) 169.00 ( 29.29%)
> Amean total-odr0-32 229.00 ( 0.00%) 162.69 ( 28.96%)
> Amean total-odr0-64 211.38 ( 0.00%) 159.00 ( 24.78%)
> Amean total-odr0-128 223.00 ( 0.00%) 160.00 ( 28.25%)
> Amean total-odr0-256 216.62 ( 0.00%) 182.00 ( 15.98%)
> Amean total-odr0-512 244.31 ( 0.00%) 186.46 ( 23.68%)
> Amean total-odr0-1024 254.54 ( 0.00%) 198.69 ( 21.94%)
> Amean total-odr0-2048 264.08 ( 0.00%) 208.00 ( 21.24%)
> Amean total-odr0-4096 277.38 ( 0.00%) 219.00 ( 21.05%)
> Amean total-odr0-8192 279.00 ( 0.00%) 220.92 ( 20.82%)
> Amean total-odr0-16384 269.38 ( 0.00%) 219.92 ( 18.36%)
>
> This is the alloc, free and total overhead of allocating order-0 pages in
> batches of 1 page up to 16384 pages. Avoiding disabling/enabling overhead
> massively reduces overhead. Alloc overhead is roughly reduced by 14-20% in
> most cases. The free path is reduced by 26-46% and the total reduction
> is significant.
>
[...]
>
> Similarly, little benefit was seen on networking benchmarks both localhost
> and between physical server/clients where other costs dominate. It's
> possible that this will only be noticable on very high speed networks.
The networking results highly depend on NIC drivers. As you mention in
the cover-letter, (1) some drivers (e.g mlx4) alloc high-order pages to
work-around order-0 pages and DMA-map being too slow (for their HW
use-case), (2) drivers that do use order-0 pages have driver specific
page-recycling tricks (e.g. mlx5 and ixgbe). The page_pool target
making a more generic recycle mechanism for drivers to use.
I'm very excited to see improvements in this area! :-)))
--
Best regards,
Jesper Dangaard Brouer
MSc.CS, Principal Kernel Engineer at Red Hat
LinkedIn: http://www.linkedin.com/in/brouer
^ permalink raw reply [flat|nested] 26+ messages in thread
* Re: [PATCH 3/4] mm, page_allocator: Only use per-cpu allocator for irq-safe requests
@ 2017-01-04 14:20 ` Jesper Dangaard Brouer
0 siblings, 0 replies; 26+ messages in thread
From: Jesper Dangaard Brouer @ 2017-01-04 14:20 UTC (permalink / raw)
To: Mel Gorman; +Cc: Linux Kernel, Linux-MM, brouer
On Wed, 4 Jan 2017 11:10:48 +0000 Mel Gorman <mgorman@techsingularity.net> wrote:
> Many workloads that allocate pages are not handling an interrupt at a
> time. As allocation requests may be from IRQ context, it's necessary to
> disable/enable IRQs for every page allocation. This cost is the bulk
> of the free path but also a significant percentage of the allocation
> path.
>
> This patch alters the locking and checks such that only irq-safe allocation
> requests use the per-cpu allocator. All others acquire the irq-safe
> zone->lock and allocate from the buddy allocator. It relies on disabling
> preemption to safely access the per-cpu structures.
I love this idea and patch :-)
> It could be slightly
> modified to avoid soft IRQs using it but it's not clear it's worthwhile.
NICs usually refill their RX-ring from SoftIRQ context (NAPI).
Thus, we do want this optimization to work in softirq.
> This modification may slow allocations from IRQ context slightly but the main
> gain from the per-cpu allocator is that it scales better for allocations
> from multiple contexts. There is an implicit assumption that intensive
> allocations from IRQ contexts on multiple CPUs from a single NUMA node are
> rare and that the fast majority of scaling issues are encountered in !IRQ
> contexts such as page faulting.
IHMO, I agree with this implicit assumption.
> It's worth noting that this patch is not
> required for a bulk page allocator but it significantly reduces the overhead.
>
> The following is results from a page allocator micro-benchmark. Only
> order-0 is interesting as higher orders do not use the per-cpu allocator
I'm seeing approx 34% reduction in a order-0 micro-benchmark! amazing! :-)
[1] https://github.com/netoptimizer/prototype-kernel/blob/master/kernel/mm/bench/
> 4.10.0-rc2 4.10.0-rc2
> vanilla irqsafe-v1r5
> Amean alloc-odr0-1 287.15 ( 0.00%) 219.00 ( 23.73%)
> Amean alloc-odr0-2 221.23 ( 0.00%) 183.23 ( 17.18%)
> Amean alloc-odr0-4 187.00 ( 0.00%) 151.38 ( 19.05%)
> Amean alloc-odr0-8 167.54 ( 0.00%) 132.77 ( 20.75%)
> Amean alloc-odr0-16 156.00 ( 0.00%) 123.00 ( 21.15%)
> Amean alloc-odr0-32 149.00 ( 0.00%) 118.31 ( 20.60%)
> Amean alloc-odr0-64 138.77 ( 0.00%) 116.00 ( 16.41%)
> Amean alloc-odr0-128 145.00 ( 0.00%) 118.00 ( 18.62%)
> Amean alloc-odr0-256 136.15 ( 0.00%) 125.00 ( 8.19%)
> Amean alloc-odr0-512 147.92 ( 0.00%) 121.77 ( 17.68%)
> Amean alloc-odr0-1024 147.23 ( 0.00%) 126.15 ( 14.32%)
> Amean alloc-odr0-2048 155.15 ( 0.00%) 129.92 ( 16.26%)
> Amean alloc-odr0-4096 164.00 ( 0.00%) 136.77 ( 16.60%)
> Amean alloc-odr0-8192 166.92 ( 0.00%) 138.08 ( 17.28%)
> Amean alloc-odr0-16384 159.00 ( 0.00%) 138.00 ( 13.21%)
> Amean free-odr0-1 165.00 ( 0.00%) 89.00 ( 46.06%)
> Amean free-odr0-2 113.00 ( 0.00%) 63.00 ( 44.25%)
> Amean free-odr0-4 99.00 ( 0.00%) 54.00 ( 45.45%)
> Amean free-odr0-8 88.00 ( 0.00%) 47.38 ( 46.15%)
> Amean free-odr0-16 83.00 ( 0.00%) 46.00 ( 44.58%)
> Amean free-odr0-32 80.00 ( 0.00%) 44.38 ( 44.52%)
> Amean free-odr0-64 72.62 ( 0.00%) 43.00 ( 40.78%)
> Amean free-odr0-128 78.00 ( 0.00%) 42.00 ( 46.15%)
> Amean free-odr0-256 80.46 ( 0.00%) 57.00 ( 29.16%)
> Amean free-odr0-512 96.38 ( 0.00%) 64.69 ( 32.88%)
> Amean free-odr0-1024 107.31 ( 0.00%) 72.54 ( 32.40%)
> Amean free-odr0-2048 108.92 ( 0.00%) 78.08 ( 28.32%)
> Amean free-odr0-4096 113.38 ( 0.00%) 82.23 ( 27.48%)
> Amean free-odr0-8192 112.08 ( 0.00%) 82.85 ( 26.08%)
> Amean free-odr0-16384 110.38 ( 0.00%) 81.92 ( 25.78%)
> Amean total-odr0-1 452.15 ( 0.00%) 308.00 ( 31.88%)
> Amean total-odr0-2 334.23 ( 0.00%) 246.23 ( 26.33%)
> Amean total-odr0-4 286.00 ( 0.00%) 205.38 ( 28.19%)
> Amean total-odr0-8 255.54 ( 0.00%) 180.15 ( 29.50%)
> Amean total-odr0-16 239.00 ( 0.00%) 169.00 ( 29.29%)
> Amean total-odr0-32 229.00 ( 0.00%) 162.69 ( 28.96%)
> Amean total-odr0-64 211.38 ( 0.00%) 159.00 ( 24.78%)
> Amean total-odr0-128 223.00 ( 0.00%) 160.00 ( 28.25%)
> Amean total-odr0-256 216.62 ( 0.00%) 182.00 ( 15.98%)
> Amean total-odr0-512 244.31 ( 0.00%) 186.46 ( 23.68%)
> Amean total-odr0-1024 254.54 ( 0.00%) 198.69 ( 21.94%)
> Amean total-odr0-2048 264.08 ( 0.00%) 208.00 ( 21.24%)
> Amean total-odr0-4096 277.38 ( 0.00%) 219.00 ( 21.05%)
> Amean total-odr0-8192 279.00 ( 0.00%) 220.92 ( 20.82%)
> Amean total-odr0-16384 269.38 ( 0.00%) 219.92 ( 18.36%)
>
> This is the alloc, free and total overhead of allocating order-0 pages in
> batches of 1 page up to 16384 pages. Avoiding disabling/enabling overhead
> massively reduces overhead. Alloc overhead is roughly reduced by 14-20% in
> most cases. The free path is reduced by 26-46% and the total reduction
> is significant.
>
[...]
>
> Similarly, little benefit was seen on networking benchmarks both localhost
> and between physical server/clients where other costs dominate. It's
> possible that this will only be noticable on very high speed networks.
The networking results highly depend on NIC drivers. As you mention in
the cover-letter, (1) some drivers (e.g mlx4) alloc high-order pages to
work-around order-0 pages and DMA-map being too slow (for their HW
use-case), (2) drivers that do use order-0 pages have driver specific
page-recycling tricks (e.g. mlx5 and ixgbe). The page_pool target
making a more generic recycle mechanism for drivers to use.
I'm very excited to see improvements in this area! :-)))
--
Best regards,
Jesper Dangaard Brouer
MSc.CS, Principal Kernel Engineer at Red Hat
LinkedIn: http://www.linkedin.com/in/brouer
--
To unsubscribe, send a message with 'unsubscribe linux-mm' in
the body to majordomo@kvack.org. For more info on Linux MM,
see: http://www.linux-mm.org/ .
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^ permalink raw reply [flat|nested] 26+ messages in thread
* Re: [PATCH 3/4] mm, page_allocator: Only use per-cpu allocator for irq-safe requests
2017-01-04 11:10 ` Mel Gorman
@ 2017-01-06 3:26 ` Hillf Danton
-1 siblings, 0 replies; 26+ messages in thread
From: Hillf Danton @ 2017-01-06 3:26 UTC (permalink / raw)
To: 'Mel Gorman', 'Jesper Dangaard Brouer'
Cc: 'Linux Kernel', 'Linux-MM'
On Wednesday, January 04, 2017 7:11 PM Mel Gorman wrote:
> @@ -2647,9 +2644,8 @@ static struct page *rmqueue_pcplist(struct zone *preferred_zone,
> struct list_head *list;
> bool cold = ((gfp_flags & __GFP_COLD) != 0);
> struct page *page;
> - unsigned long flags;
>
> - local_irq_save(flags);
> + preempt_disable();
> pcp = &this_cpu_ptr(zone->pageset)->pcp;
> list = &pcp->lists[migratetype];
> page = __rmqueue_pcplist(zone, order, gfp_flags, migratetype,
> @@ -2658,7 +2654,7 @@ static struct page *rmqueue_pcplist(struct zone *preferred_zone,
> __count_zid_vm_events(PGALLOC, page_zonenum(page), 1 << order);
> zone_statistics(preferred_zone, zone, gfp_flags);
> }
> - local_irq_restore(flags);
> + preempt_enable();
> return page;
> }
>
With PREEMPT configured, preempt_enable() adds entry point to schedule().
Is that needed when we try to allocate a page?
Hillf
^ permalink raw reply [flat|nested] 26+ messages in thread
* Re: [PATCH 3/4] mm, page_allocator: Only use per-cpu allocator for irq-safe requests
@ 2017-01-06 3:26 ` Hillf Danton
0 siblings, 0 replies; 26+ messages in thread
From: Hillf Danton @ 2017-01-06 3:26 UTC (permalink / raw)
To: 'Mel Gorman', 'Jesper Dangaard Brouer'
Cc: 'Linux Kernel', 'Linux-MM'
On Wednesday, January 04, 2017 7:11 PM Mel Gorman wrote:
> @@ -2647,9 +2644,8 @@ static struct page *rmqueue_pcplist(struct zone *preferred_zone,
> struct list_head *list;
> bool cold = ((gfp_flags & __GFP_COLD) != 0);
> struct page *page;
> - unsigned long flags;
>
> - local_irq_save(flags);
> + preempt_disable();
> pcp = &this_cpu_ptr(zone->pageset)->pcp;
> list = &pcp->lists[migratetype];
> page = __rmqueue_pcplist(zone, order, gfp_flags, migratetype,
> @@ -2658,7 +2654,7 @@ static struct page *rmqueue_pcplist(struct zone *preferred_zone,
> __count_zid_vm_events(PGALLOC, page_zonenum(page), 1 << order);
> zone_statistics(preferred_zone, zone, gfp_flags);
> }
> - local_irq_restore(flags);
> + preempt_enable();
> return page;
> }
>
With PREEMPT configured, preempt_enable() adds entry point to schedule().
Is that needed when we try to allocate a page?
Hillf
--
To unsubscribe, send a message with 'unsubscribe linux-mm' in
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^ permalink raw reply [flat|nested] 26+ messages in thread
* Re: [PATCH 3/4] mm, page_allocator: Only use per-cpu allocator for irq-safe requests
2017-01-06 3:26 ` Hillf Danton
@ 2017-01-06 10:15 ` Mel Gorman
-1 siblings, 0 replies; 26+ messages in thread
From: Mel Gorman @ 2017-01-06 10:15 UTC (permalink / raw)
To: Hillf Danton
Cc: 'Jesper Dangaard Brouer', 'Linux Kernel',
'Linux-MM'
On Fri, Jan 06, 2017 at 11:26:46AM +0800, Hillf Danton wrote:
>
> On Wednesday, January 04, 2017 7:11 PM Mel Gorman wrote:
> > @@ -2647,9 +2644,8 @@ static struct page *rmqueue_pcplist(struct zone *preferred_zone,
> > struct list_head *list;
> > bool cold = ((gfp_flags & __GFP_COLD) != 0);
> > struct page *page;
> > - unsigned long flags;
> >
> > - local_irq_save(flags);
> > + preempt_disable();
> > pcp = &this_cpu_ptr(zone->pageset)->pcp;
> > list = &pcp->lists[migratetype];
> > page = __rmqueue_pcplist(zone, order, gfp_flags, migratetype,
> > @@ -2658,7 +2654,7 @@ static struct page *rmqueue_pcplist(struct zone *preferred_zone,
> > __count_zid_vm_events(PGALLOC, page_zonenum(page), 1 << order);
> > zone_statistics(preferred_zone, zone, gfp_flags);
> > }
> > - local_irq_restore(flags);
> > + preempt_enable();
> > return page;
> > }
> >
> With PREEMPT configured, preempt_enable() adds entry point to schedule().
> Is that needed when we try to allocate a page?
>
Not necessarily but what are you proposing as an alternative? get_cpu()
is not an alternative and the point is to avoid disabling interrupts
which is a much more expensive operation.
--
Mel Gorman
SUSE Labs
^ permalink raw reply [flat|nested] 26+ messages in thread
* Re: [PATCH 3/4] mm, page_allocator: Only use per-cpu allocator for irq-safe requests
@ 2017-01-06 10:15 ` Mel Gorman
0 siblings, 0 replies; 26+ messages in thread
From: Mel Gorman @ 2017-01-06 10:15 UTC (permalink / raw)
To: Hillf Danton
Cc: 'Jesper Dangaard Brouer', 'Linux Kernel',
'Linux-MM'
On Fri, Jan 06, 2017 at 11:26:46AM +0800, Hillf Danton wrote:
>
> On Wednesday, January 04, 2017 7:11 PM Mel Gorman wrote:
> > @@ -2647,9 +2644,8 @@ static struct page *rmqueue_pcplist(struct zone *preferred_zone,
> > struct list_head *list;
> > bool cold = ((gfp_flags & __GFP_COLD) != 0);
> > struct page *page;
> > - unsigned long flags;
> >
> > - local_irq_save(flags);
> > + preempt_disable();
> > pcp = &this_cpu_ptr(zone->pageset)->pcp;
> > list = &pcp->lists[migratetype];
> > page = __rmqueue_pcplist(zone, order, gfp_flags, migratetype,
> > @@ -2658,7 +2654,7 @@ static struct page *rmqueue_pcplist(struct zone *preferred_zone,
> > __count_zid_vm_events(PGALLOC, page_zonenum(page), 1 << order);
> > zone_statistics(preferred_zone, zone, gfp_flags);
> > }
> > - local_irq_restore(flags);
> > + preempt_enable();
> > return page;
> > }
> >
> With PREEMPT configured, preempt_enable() adds entry point to schedule().
> Is that needed when we try to allocate a page?
>
Not necessarily but what are you proposing as an alternative? get_cpu()
is not an alternative and the point is to avoid disabling interrupts
which is a much more expensive operation.
--
Mel Gorman
SUSE Labs
--
To unsubscribe, send a message with 'unsubscribe linux-mm' in
the body to majordomo@kvack.org. For more info on Linux MM,
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^ permalink raw reply [flat|nested] 26+ messages in thread
* Re: [PATCH 3/4] mm, page_allocator: Only use per-cpu allocator for irq-safe requests
2017-01-06 10:15 ` Mel Gorman
@ 2017-01-09 3:14 ` Hillf Danton
-1 siblings, 0 replies; 26+ messages in thread
From: Hillf Danton @ 2017-01-09 3:14 UTC (permalink / raw)
To: 'Mel Gorman'
Cc: 'Jesper Dangaard Brouer', 'Linux Kernel',
'Linux-MM'
> Sent: Friday, January 06, 2017 6:16 PM Mel Gorman wrote:
>
> On Fri, Jan 06, 2017 at 11:26:46AM +0800, Hillf Danton wrote:
> >
> > On Wednesday, January 04, 2017 7:11 PM Mel Gorman wrote:
> > > @@ -2647,9 +2644,8 @@ static struct page *rmqueue_pcplist(struct zone *preferred_zone,
> > > struct list_head *list;
> > > bool cold = ((gfp_flags & __GFP_COLD) != 0);
> > > struct page *page;
> > > - unsigned long flags;
> > >
> > > - local_irq_save(flags);
> > > + preempt_disable();
> > > pcp = &this_cpu_ptr(zone->pageset)->pcp;
> > > list = &pcp->lists[migratetype];
> > > page = __rmqueue_pcplist(zone, order, gfp_flags, migratetype,
> > > @@ -2658,7 +2654,7 @@ static struct page *rmqueue_pcplist(struct zone *preferred_zone,
> > > __count_zid_vm_events(PGALLOC, page_zonenum(page), 1 << order);
> > > zone_statistics(preferred_zone, zone, gfp_flags);
> > > }
> > > - local_irq_restore(flags);
> > > + preempt_enable();
> > > return page;
> > > }
> > >
> > With PREEMPT configured, preempt_enable() adds entry point to schedule().
> > Is that needed when we try to allocate a page?
> >
>
> Not necessarily but what are you proposing as an alternative?
preempt_enable_no_resched() looks at first glance a choice for us to
avoid flipping interrupts.
> get_cpu()
> is not an alternative and the point is to avoid disabling interrupts
> which is a much more expensive operation.
>
Agree with every word.
Hillf
^ permalink raw reply [flat|nested] 26+ messages in thread
* Re: [PATCH 3/4] mm, page_allocator: Only use per-cpu allocator for irq-safe requests
@ 2017-01-09 3:14 ` Hillf Danton
0 siblings, 0 replies; 26+ messages in thread
From: Hillf Danton @ 2017-01-09 3:14 UTC (permalink / raw)
To: 'Mel Gorman'
Cc: 'Jesper Dangaard Brouer', 'Linux Kernel',
'Linux-MM'
> Sent: Friday, January 06, 2017 6:16 PM Mel Gorman wrote:
>
> On Fri, Jan 06, 2017 at 11:26:46AM +0800, Hillf Danton wrote:
> >
> > On Wednesday, January 04, 2017 7:11 PM Mel Gorman wrote:
> > > @@ -2647,9 +2644,8 @@ static struct page *rmqueue_pcplist(struct zone *preferred_zone,
> > > struct list_head *list;
> > > bool cold = ((gfp_flags & __GFP_COLD) != 0);
> > > struct page *page;
> > > - unsigned long flags;
> > >
> > > - local_irq_save(flags);
> > > + preempt_disable();
> > > pcp = &this_cpu_ptr(zone->pageset)->pcp;
> > > list = &pcp->lists[migratetype];
> > > page = __rmqueue_pcplist(zone, order, gfp_flags, migratetype,
> > > @@ -2658,7 +2654,7 @@ static struct page *rmqueue_pcplist(struct zone *preferred_zone,
> > > __count_zid_vm_events(PGALLOC, page_zonenum(page), 1 << order);
> > > zone_statistics(preferred_zone, zone, gfp_flags);
> > > }
> > > - local_irq_restore(flags);
> > > + preempt_enable();
> > > return page;
> > > }
> > >
> > With PREEMPT configured, preempt_enable() adds entry point to schedule().
> > Is that needed when we try to allocate a page?
> >
>
> Not necessarily but what are you proposing as an alternative?
preempt_enable_no_resched() looks at first glance a choice for us to
avoid flipping interrupts.
> get_cpu()
> is not an alternative and the point is to avoid disabling interrupts
> which is a much more expensive operation.
>
Agree with every word.
Hillf
--
To unsubscribe, send a message with 'unsubscribe linux-mm' in
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see: http://www.linux-mm.org/ .
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^ permalink raw reply [flat|nested] 26+ messages in thread
* Re: [PATCH 3/4] mm, page_allocator: Only use per-cpu allocator for irq-safe requests
2017-01-09 3:14 ` Hillf Danton
@ 2017-01-09 9:48 ` Mel Gorman
-1 siblings, 0 replies; 26+ messages in thread
From: Mel Gorman @ 2017-01-09 9:48 UTC (permalink / raw)
To: Hillf Danton
Cc: 'Jesper Dangaard Brouer', 'Linux Kernel',
'Linux-MM'
On Mon, Jan 09, 2017 at 11:14:29AM +0800, Hillf Danton wrote:
> > Sent: Friday, January 06, 2017 6:16 PM Mel Gorman wrote:
> >
> > On Fri, Jan 06, 2017 at 11:26:46AM +0800, Hillf Danton wrote:
> > >
> > > On Wednesday, January 04, 2017 7:11 PM Mel Gorman wrote:
> > > > @@ -2647,9 +2644,8 @@ static struct page *rmqueue_pcplist(struct zone *preferred_zone,
> > > > struct list_head *list;
> > > > bool cold = ((gfp_flags & __GFP_COLD) != 0);
> > > > struct page *page;
> > > > - unsigned long flags;
> > > >
> > > > - local_irq_save(flags);
> > > > + preempt_disable();
> > > > pcp = &this_cpu_ptr(zone->pageset)->pcp;
> > > > list = &pcp->lists[migratetype];
> > > > page = __rmqueue_pcplist(zone, order, gfp_flags, migratetype,
> > > > @@ -2658,7 +2654,7 @@ static struct page *rmqueue_pcplist(struct zone *preferred_zone,
> > > > __count_zid_vm_events(PGALLOC, page_zonenum(page), 1 << order);
> > > > zone_statistics(preferred_zone, zone, gfp_flags);
> > > > }
> > > > - local_irq_restore(flags);
> > > > + preempt_enable();
> > > > return page;
> > > > }
> > > >
> > > With PREEMPT configured, preempt_enable() adds entry point to schedule().
> > > Is that needed when we try to allocate a page?
> > >
> >
> > Not necessarily but what are you proposing as an alternative?
>
> preempt_enable_no_resched() looks at first glance a choice for us to
> avoid flipping interrupts.
>
Ok, I wasn't sure if you were proposing something more drastic. I can
make it this although I have no reason to believe it will really matter.
The path should be short enough that it's unlikely a scheduler event
would ever occur at that point. Still, no harm in doing what you
suggest.
Thanks.
--
Mel Gorman
SUSE Labs
^ permalink raw reply [flat|nested] 26+ messages in thread
* Re: [PATCH 3/4] mm, page_allocator: Only use per-cpu allocator for irq-safe requests
@ 2017-01-09 9:48 ` Mel Gorman
0 siblings, 0 replies; 26+ messages in thread
From: Mel Gorman @ 2017-01-09 9:48 UTC (permalink / raw)
To: Hillf Danton
Cc: 'Jesper Dangaard Brouer', 'Linux Kernel',
'Linux-MM'
On Mon, Jan 09, 2017 at 11:14:29AM +0800, Hillf Danton wrote:
> > Sent: Friday, January 06, 2017 6:16 PM Mel Gorman wrote:
> >
> > On Fri, Jan 06, 2017 at 11:26:46AM +0800, Hillf Danton wrote:
> > >
> > > On Wednesday, January 04, 2017 7:11 PM Mel Gorman wrote:
> > > > @@ -2647,9 +2644,8 @@ static struct page *rmqueue_pcplist(struct zone *preferred_zone,
> > > > struct list_head *list;
> > > > bool cold = ((gfp_flags & __GFP_COLD) != 0);
> > > > struct page *page;
> > > > - unsigned long flags;
> > > >
> > > > - local_irq_save(flags);
> > > > + preempt_disable();
> > > > pcp = &this_cpu_ptr(zone->pageset)->pcp;
> > > > list = &pcp->lists[migratetype];
> > > > page = __rmqueue_pcplist(zone, order, gfp_flags, migratetype,
> > > > @@ -2658,7 +2654,7 @@ static struct page *rmqueue_pcplist(struct zone *preferred_zone,
> > > > __count_zid_vm_events(PGALLOC, page_zonenum(page), 1 << order);
> > > > zone_statistics(preferred_zone, zone, gfp_flags);
> > > > }
> > > > - local_irq_restore(flags);
> > > > + preempt_enable();
> > > > return page;
> > > > }
> > > >
> > > With PREEMPT configured, preempt_enable() adds entry point to schedule().
> > > Is that needed when we try to allocate a page?
> > >
> >
> > Not necessarily but what are you proposing as an alternative?
>
> preempt_enable_no_resched() looks at first glance a choice for us to
> avoid flipping interrupts.
>
Ok, I wasn't sure if you were proposing something more drastic. I can
make it this although I have no reason to believe it will really matter.
The path should be short enough that it's unlikely a scheduler event
would ever occur at that point. Still, no harm in doing what you
suggest.
Thanks.
--
Mel Gorman
SUSE Labs
--
To unsubscribe, send a message with 'unsubscribe linux-mm' in
the body to majordomo@kvack.org. For more info on Linux MM,
see: http://www.linux-mm.org/ .
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^ permalink raw reply [flat|nested] 26+ messages in thread
* Re: [PATCH 3/4] mm, page_allocator: Only use per-cpu allocator for irq-safe requests
2017-01-09 9:48 ` Mel Gorman
@ 2017-01-09 9:55 ` Hillf Danton
-1 siblings, 0 replies; 26+ messages in thread
From: Hillf Danton @ 2017-01-09 9:55 UTC (permalink / raw)
To: 'Mel Gorman'
Cc: 'Jesper Dangaard Brouer', 'Linux Kernel',
'Linux-MM'
On Monday, January 09, 2017 5:48 PM Mel Gorman wrote:
> On Mon, Jan 09, 2017 at 11:14:29AM +0800, Hillf Danton wrote:
> > > On Friday, January 06, 2017 6:16 PM Mel Gorman wrote:
> > >
> > > On Fri, Jan 06, 2017 at 11:26:46AM +0800, Hillf Danton wrote:
> > > >
> > > > On Wednesday, January 04, 2017 7:11 PM Mel Gorman wrote:
> > > > > @@ -2647,9 +2644,8 @@ static struct page *rmqueue_pcplist(struct zone *preferred_zone,
> > > > > struct list_head *list;
> > > > > bool cold = ((gfp_flags & __GFP_COLD) != 0);
> > > > > struct page *page;
> > > > > - unsigned long flags;
> > > > >
> > > > > - local_irq_save(flags);
> > > > > + preempt_disable();
> > > > > pcp = &this_cpu_ptr(zone->pageset)->pcp;
> > > > > list = &pcp->lists[migratetype];
> > > > > page = __rmqueue_pcplist(zone, order, gfp_flags, migratetype,
> > > > > @@ -2658,7 +2654,7 @@ static struct page *rmqueue_pcplist(struct zone *preferred_zone,
> > > > > __count_zid_vm_events(PGALLOC, page_zonenum(page), 1 << order);
> > > > > zone_statistics(preferred_zone, zone, gfp_flags);
> > > > > }
> > > > > - local_irq_restore(flags);
> > > > > + preempt_enable();
> > > > > return page;
> > > > > }
> > > > >
> > > > With PREEMPT configured, preempt_enable() adds entry point to schedule().
> > > > Is that needed when we try to allocate a page?
> > > >
> > >
> > > Not necessarily but what are you proposing as an alternative?
> >
> > preempt_enable_no_resched() looks at first glance a choice for us to
> > avoid flipping interrupts.
> >
>
> Ok, I wasn't sure if you were proposing something more drastic. I can
> make it this although I have no reason to believe it will really matter.
> The path should be short enough that it's unlikely a scheduler event
> would ever occur at that point. Still, no harm in doing what you
> suggest.
>
If spin, feel free to add
Acked-by: Hillf Danton <hillf.zj@alibaba-inc.com>
to the patchset.
^ permalink raw reply [flat|nested] 26+ messages in thread
* Re: [PATCH 3/4] mm, page_allocator: Only use per-cpu allocator for irq-safe requests
@ 2017-01-09 9:55 ` Hillf Danton
0 siblings, 0 replies; 26+ messages in thread
From: Hillf Danton @ 2017-01-09 9:55 UTC (permalink / raw)
To: 'Mel Gorman'
Cc: 'Jesper Dangaard Brouer', 'Linux Kernel',
'Linux-MM'
On Monday, January 09, 2017 5:48 PM Mel Gorman wrote:
> On Mon, Jan 09, 2017 at 11:14:29AM +0800, Hillf Danton wrote:
> > > On Friday, January 06, 2017 6:16 PM Mel Gorman wrote:
> > >
> > > On Fri, Jan 06, 2017 at 11:26:46AM +0800, Hillf Danton wrote:
> > > >
> > > > On Wednesday, January 04, 2017 7:11 PM Mel Gorman wrote:
> > > > > @@ -2647,9 +2644,8 @@ static struct page *rmqueue_pcplist(struct zone *preferred_zone,
> > > > > struct list_head *list;
> > > > > bool cold = ((gfp_flags & __GFP_COLD) != 0);
> > > > > struct page *page;
> > > > > - unsigned long flags;
> > > > >
> > > > > - local_irq_save(flags);
> > > > > + preempt_disable();
> > > > > pcp = &this_cpu_ptr(zone->pageset)->pcp;
> > > > > list = &pcp->lists[migratetype];
> > > > > page = __rmqueue_pcplist(zone, order, gfp_flags, migratetype,
> > > > > @@ -2658,7 +2654,7 @@ static struct page *rmqueue_pcplist(struct zone *preferred_zone,
> > > > > __count_zid_vm_events(PGALLOC, page_zonenum(page), 1 << order);
> > > > > zone_statistics(preferred_zone, zone, gfp_flags);
> > > > > }
> > > > > - local_irq_restore(flags);
> > > > > + preempt_enable();
> > > > > return page;
> > > > > }
> > > > >
> > > > With PREEMPT configured, preempt_enable() adds entry point to schedule().
> > > > Is that needed when we try to allocate a page?
> > > >
> > >
> > > Not necessarily but what are you proposing as an alternative?
> >
> > preempt_enable_no_resched() looks at first glance a choice for us to
> > avoid flipping interrupts.
> >
>
> Ok, I wasn't sure if you were proposing something more drastic. I can
> make it this although I have no reason to believe it will really matter.
> The path should be short enough that it's unlikely a scheduler event
> would ever occur at that point. Still, no harm in doing what you
> suggest.
>
If spin, feel free to add
Acked-by: Hillf Danton <hillf.zj@alibaba-inc.com>
to the patchset.
--
To unsubscribe, send a message with 'unsubscribe linux-mm' in
the body to majordomo@kvack.org. For more info on Linux MM,
see: http://www.linux-mm.org/ .
Don't email: <a href=mailto:"dont@kvack.org"> email@kvack.org </a>
^ permalink raw reply [flat|nested] 26+ messages in thread
* [PATCH 4/4] mm, page_alloc: Add a bulk page allocator
2017-01-04 11:10 ` Mel Gorman
@ 2017-01-04 11:10 ` Mel Gorman
-1 siblings, 0 replies; 26+ messages in thread
From: Mel Gorman @ 2017-01-04 11:10 UTC (permalink / raw)
To: Jesper Dangaard Brouer; +Cc: Linux Kernel, Linux-MM, Mel Gorman
This patch adds a new page allocator interface via alloc_pages_bulk,
__alloc_pages_bulk and __alloc_pages_bulk_nodemask. A caller requests
a number of pages to be allocated and added to a list. They can be
freed in bulk using free_hot_cold_page_list.
The API is not guaranteed to return the requested number of pages and
may fail if the preferred allocation zone has limited free memory,
the cpuset changes during the allocation or page debugging decides
to fail an allocation. It's up to the caller to request more pages
in batch if necessary.
Signed-off-by: Mel Gorman <mgorman@techsingularity.net>
---
include/linux/gfp.h | 23 ++++++++++++++
mm/page_alloc.c | 92 +++++++++++++++++++++++++++++++++++++++++++++++++++++
2 files changed, 115 insertions(+)
diff --git a/include/linux/gfp.h b/include/linux/gfp.h
index 4175dca4ac39..1da3a9a48701 100644
--- a/include/linux/gfp.h
+++ b/include/linux/gfp.h
@@ -433,6 +433,29 @@ __alloc_pages(gfp_t gfp_mask, unsigned int order,
return __alloc_pages_nodemask(gfp_mask, order, zonelist, NULL);
}
+unsigned long
+__alloc_pages_bulk_nodemask(gfp_t gfp_mask, unsigned int order,
+ struct zonelist *zonelist, nodemask_t *nodemask,
+ unsigned long nr_pages, struct list_head *alloc_list);
+
+static inline unsigned long
+__alloc_pages_bulk(gfp_t gfp_mask, unsigned int order,
+ struct zonelist *zonelist, unsigned long nr_pages,
+ struct list_head *list)
+{
+ return __alloc_pages_bulk_nodemask(gfp_mask, order, zonelist, NULL,
+ nr_pages, list);
+}
+
+static inline unsigned long
+alloc_pages_bulk(gfp_t gfp_mask, unsigned int order,
+ unsigned long nr_pages, struct list_head *list)
+{
+ int nid = numa_mem_id();
+ return __alloc_pages_bulk(gfp_mask, order,
+ node_zonelist(nid, gfp_mask), nr_pages, list);
+}
+
/*
* Allocate pages, preferring the node given as nid. The node must be valid and
* online. For more general interface, see alloc_pages_node().
diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index 01b09f9da288..307ad4299dec 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -3887,6 +3887,98 @@ __alloc_pages_nodemask(gfp_t gfp_mask, unsigned int order,
EXPORT_SYMBOL(__alloc_pages_nodemask);
/*
+ * This is a batched version of the page allocator that attempts to
+ * allocate nr_pages quickly from the preferred zone and add them to list.
+ * Note that there is no guarantee that nr_pages will be allocated although
+ * every effort will be made to allocate at least one. Unlike the core
+ * allocator, no special effort is made to recover from transient
+ * failures caused by changes in cpusets.
+ */
+unsigned long
+__alloc_pages_bulk_nodemask(gfp_t gfp_mask, unsigned int order,
+ struct zonelist *zonelist, nodemask_t *nodemask,
+ unsigned long nr_pages, struct list_head *alloc_list)
+{
+ struct page *page;
+ unsigned long alloced = 0;
+ unsigned int alloc_flags = ALLOC_WMARK_LOW;
+ struct zone *zone;
+ struct per_cpu_pages *pcp;
+ struct list_head *pcp_list;
+ unsigned long flags;
+ int migratetype;
+ gfp_t alloc_mask = gfp_mask; /* The gfp_t that was actually used for allocation */
+ struct alloc_context ac = { };
+ bool cold = ((gfp_mask & __GFP_COLD) != 0);
+
+ /* If there are already pages on the list, don't bother */
+ if (!list_empty(alloc_list))
+ return 0;
+
+ /* Only handle bulk allocation of order-0 */
+ if (order)
+ goto failed;
+
+ gfp_mask &= gfp_allowed_mask;
+ if (!prepare_alloc_pages(gfp_mask, order, zonelist, nodemask, &ac, &alloc_mask, &alloc_flags))
+ return 0;
+
+ finalise_ac(gfp_mask, order, &ac);
+ if (!ac.preferred_zoneref)
+ return 0;
+
+ /*
+ * Only attempt a batch allocation if watermarks on the preferred zone
+ * are safe.
+ */
+ zone = ac.preferred_zoneref->zone;
+ if (!zone_watermark_fast(zone, order, zone->watermark[ALLOC_WMARK_HIGH] + nr_pages,
+ zonelist_zone_idx(ac.preferred_zoneref), alloc_flags))
+ goto failed;
+
+ /* Attempt the batch allocation */
+ migratetype = ac.migratetype;
+
+ local_irq_save(flags);
+ pcp = &this_cpu_ptr(zone->pageset)->pcp;
+ pcp_list = &pcp->lists[migratetype];
+
+ while (nr_pages) {
+ page = __rmqueue_pcplist(zone, order, gfp_mask, migratetype,
+ cold, pcp, pcp_list);
+ if (!page)
+ break;
+
+ nr_pages--;
+ alloced++;
+ list_add(&page->lru, alloc_list);
+ }
+
+ if (!alloced) {
+ local_irq_restore(flags);
+ preempt_enable();
+ goto failed;
+ }
+
+ __count_zid_vm_events(PGALLOC, zone_idx(zone), alloced);
+ zone_statistics(zone, zone, gfp_mask);
+
+ local_irq_restore(flags);
+
+ return alloced;
+
+failed:
+ page = __alloc_pages_nodemask(gfp_mask, order, zonelist, nodemask);
+ if (page) {
+ alloced++;
+ list_add(&page->lru, alloc_list);
+ }
+
+ return alloced;
+}
+EXPORT_SYMBOL(__alloc_pages_bulk_nodemask);
+
+/*
* Common helper functions.
*/
unsigned long __get_free_pages(gfp_t gfp_mask, unsigned int order)
--
2.11.0
^ permalink raw reply related [flat|nested] 26+ messages in thread* [PATCH 4/4] mm, page_alloc: Add a bulk page allocator
@ 2017-01-04 11:10 ` Mel Gorman
0 siblings, 0 replies; 26+ messages in thread
From: Mel Gorman @ 2017-01-04 11:10 UTC (permalink / raw)
To: Jesper Dangaard Brouer; +Cc: Linux Kernel, Linux-MM, Mel Gorman
This patch adds a new page allocator interface via alloc_pages_bulk,
__alloc_pages_bulk and __alloc_pages_bulk_nodemask. A caller requests
a number of pages to be allocated and added to a list. They can be
freed in bulk using free_hot_cold_page_list.
The API is not guaranteed to return the requested number of pages and
may fail if the preferred allocation zone has limited free memory,
the cpuset changes during the allocation or page debugging decides
to fail an allocation. It's up to the caller to request more pages
in batch if necessary.
Signed-off-by: Mel Gorman <mgorman@techsingularity.net>
---
include/linux/gfp.h | 23 ++++++++++++++
mm/page_alloc.c | 92 +++++++++++++++++++++++++++++++++++++++++++++++++++++
2 files changed, 115 insertions(+)
diff --git a/include/linux/gfp.h b/include/linux/gfp.h
index 4175dca4ac39..1da3a9a48701 100644
--- a/include/linux/gfp.h
+++ b/include/linux/gfp.h
@@ -433,6 +433,29 @@ __alloc_pages(gfp_t gfp_mask, unsigned int order,
return __alloc_pages_nodemask(gfp_mask, order, zonelist, NULL);
}
+unsigned long
+__alloc_pages_bulk_nodemask(gfp_t gfp_mask, unsigned int order,
+ struct zonelist *zonelist, nodemask_t *nodemask,
+ unsigned long nr_pages, struct list_head *alloc_list);
+
+static inline unsigned long
+__alloc_pages_bulk(gfp_t gfp_mask, unsigned int order,
+ struct zonelist *zonelist, unsigned long nr_pages,
+ struct list_head *list)
+{
+ return __alloc_pages_bulk_nodemask(gfp_mask, order, zonelist, NULL,
+ nr_pages, list);
+}
+
+static inline unsigned long
+alloc_pages_bulk(gfp_t gfp_mask, unsigned int order,
+ unsigned long nr_pages, struct list_head *list)
+{
+ int nid = numa_mem_id();
+ return __alloc_pages_bulk(gfp_mask, order,
+ node_zonelist(nid, gfp_mask), nr_pages, list);
+}
+
/*
* Allocate pages, preferring the node given as nid. The node must be valid and
* online. For more general interface, see alloc_pages_node().
diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index 01b09f9da288..307ad4299dec 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -3887,6 +3887,98 @@ __alloc_pages_nodemask(gfp_t gfp_mask, unsigned int order,
EXPORT_SYMBOL(__alloc_pages_nodemask);
/*
+ * This is a batched version of the page allocator that attempts to
+ * allocate nr_pages quickly from the preferred zone and add them to list.
+ * Note that there is no guarantee that nr_pages will be allocated although
+ * every effort will be made to allocate at least one. Unlike the core
+ * allocator, no special effort is made to recover from transient
+ * failures caused by changes in cpusets.
+ */
+unsigned long
+__alloc_pages_bulk_nodemask(gfp_t gfp_mask, unsigned int order,
+ struct zonelist *zonelist, nodemask_t *nodemask,
+ unsigned long nr_pages, struct list_head *alloc_list)
+{
+ struct page *page;
+ unsigned long alloced = 0;
+ unsigned int alloc_flags = ALLOC_WMARK_LOW;
+ struct zone *zone;
+ struct per_cpu_pages *pcp;
+ struct list_head *pcp_list;
+ unsigned long flags;
+ int migratetype;
+ gfp_t alloc_mask = gfp_mask; /* The gfp_t that was actually used for allocation */
+ struct alloc_context ac = { };
+ bool cold = ((gfp_mask & __GFP_COLD) != 0);
+
+ /* If there are already pages on the list, don't bother */
+ if (!list_empty(alloc_list))
+ return 0;
+
+ /* Only handle bulk allocation of order-0 */
+ if (order)
+ goto failed;
+
+ gfp_mask &= gfp_allowed_mask;
+ if (!prepare_alloc_pages(gfp_mask, order, zonelist, nodemask, &ac, &alloc_mask, &alloc_flags))
+ return 0;
+
+ finalise_ac(gfp_mask, order, &ac);
+ if (!ac.preferred_zoneref)
+ return 0;
+
+ /*
+ * Only attempt a batch allocation if watermarks on the preferred zone
+ * are safe.
+ */
+ zone = ac.preferred_zoneref->zone;
+ if (!zone_watermark_fast(zone, order, zone->watermark[ALLOC_WMARK_HIGH] + nr_pages,
+ zonelist_zone_idx(ac.preferred_zoneref), alloc_flags))
+ goto failed;
+
+ /* Attempt the batch allocation */
+ migratetype = ac.migratetype;
+
+ local_irq_save(flags);
+ pcp = &this_cpu_ptr(zone->pageset)->pcp;
+ pcp_list = &pcp->lists[migratetype];
+
+ while (nr_pages) {
+ page = __rmqueue_pcplist(zone, order, gfp_mask, migratetype,
+ cold, pcp, pcp_list);
+ if (!page)
+ break;
+
+ nr_pages--;
+ alloced++;
+ list_add(&page->lru, alloc_list);
+ }
+
+ if (!alloced) {
+ local_irq_restore(flags);
+ preempt_enable();
+ goto failed;
+ }
+
+ __count_zid_vm_events(PGALLOC, zone_idx(zone), alloced);
+ zone_statistics(zone, zone, gfp_mask);
+
+ local_irq_restore(flags);
+
+ return alloced;
+
+failed:
+ page = __alloc_pages_nodemask(gfp_mask, order, zonelist, nodemask);
+ if (page) {
+ alloced++;
+ list_add(&page->lru, alloc_list);
+ }
+
+ return alloced;
+}
+EXPORT_SYMBOL(__alloc_pages_bulk_nodemask);
+
+/*
* Common helper functions.
*/
unsigned long __get_free_pages(gfp_t gfp_mask, unsigned int order)
--
2.11.0
--
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^ permalink raw reply related [flat|nested] 26+ messages in thread* Re: [PATCH 4/4] mm, page_alloc: Add a bulk page allocator
2017-01-04 11:10 ` Mel Gorman
@ 2017-01-04 13:48 ` Jesper Dangaard Brouer
-1 siblings, 0 replies; 26+ messages in thread
From: Jesper Dangaard Brouer @ 2017-01-04 13:48 UTC (permalink / raw)
To: Mel Gorman; +Cc: Linux Kernel, Linux-MM, brouer
On Wed, 4 Jan 2017 11:10:49 +0000
Mel Gorman <mgorman@techsingularity.net> wrote:
> This patch adds a new page allocator interface via alloc_pages_bulk,
> __alloc_pages_bulk and __alloc_pages_bulk_nodemask. A caller requests
> a number of pages to be allocated and added to a list. They can be
> freed in bulk using free_hot_cold_page_list.
>
> The API is not guaranteed to return the requested number of pages and
> may fail if the preferred allocation zone has limited free memory,
> the cpuset changes during the allocation or page debugging decides
> to fail an allocation. It's up to the caller to request more pages
> in batch if necessary.
I generally like it, thanks! :-)
> Signed-off-by: Mel Gorman <mgorman@techsingularity.net>
> ---
> include/linux/gfp.h | 23 ++++++++++++++
> mm/page_alloc.c | 92 +++++++++++++++++++++++++++++++++++++++++++++++++++++
> 2 files changed, 115 insertions(+)
>
> diff --git a/include/linux/gfp.h b/include/linux/gfp.h
> index 4175dca4ac39..1da3a9a48701 100644
> --- a/include/linux/gfp.h
> +++ b/include/linux/gfp.h
> @@ -433,6 +433,29 @@ __alloc_pages(gfp_t gfp_mask, unsigned int order,
> return __alloc_pages_nodemask(gfp_mask, order, zonelist, NULL);
> }
>
> +unsigned long
> +__alloc_pages_bulk_nodemask(gfp_t gfp_mask, unsigned int order,
> + struct zonelist *zonelist, nodemask_t *nodemask,
> + unsigned long nr_pages, struct list_head *alloc_list);
> +
> +static inline unsigned long
> +__alloc_pages_bulk(gfp_t gfp_mask, unsigned int order,
> + struct zonelist *zonelist, unsigned long nr_pages,
> + struct list_head *list)
> +{
> + return __alloc_pages_bulk_nodemask(gfp_mask, order, zonelist, NULL,
> + nr_pages, list);
> +}
> +
> +static inline unsigned long
> +alloc_pages_bulk(gfp_t gfp_mask, unsigned int order,
> + unsigned long nr_pages, struct list_head *list)
> +{
> + int nid = numa_mem_id();
> + return __alloc_pages_bulk(gfp_mask, order,
> + node_zonelist(nid, gfp_mask), nr_pages, list);
> +}
> +
> /*
> * Allocate pages, preferring the node given as nid. The node must be valid and
> * online. For more general interface, see alloc_pages_node().
> diff --git a/mm/page_alloc.c b/mm/page_alloc.c
> index 01b09f9da288..307ad4299dec 100644
> --- a/mm/page_alloc.c
> +++ b/mm/page_alloc.c
> @@ -3887,6 +3887,98 @@ __alloc_pages_nodemask(gfp_t gfp_mask, unsigned int order,
> EXPORT_SYMBOL(__alloc_pages_nodemask);
>
> /*
> + * This is a batched version of the page allocator that attempts to
> + * allocate nr_pages quickly from the preferred zone and add them to list.
> + * Note that there is no guarantee that nr_pages will be allocated although
> + * every effort will be made to allocate at least one. Unlike the core
> + * allocator, no special effort is made to recover from transient
> + * failures caused by changes in cpusets.
> + */
> +unsigned long
> +__alloc_pages_bulk_nodemask(gfp_t gfp_mask, unsigned int order,
> + struct zonelist *zonelist, nodemask_t *nodemask,
> + unsigned long nr_pages, struct list_head *alloc_list)
> +{
> + struct page *page;
> + unsigned long alloced = 0;
> + unsigned int alloc_flags = ALLOC_WMARK_LOW;
> + struct zone *zone;
> + struct per_cpu_pages *pcp;
> + struct list_head *pcp_list;
> + unsigned long flags;
> + int migratetype;
> + gfp_t alloc_mask = gfp_mask; /* The gfp_t that was actually used for allocation */
> + struct alloc_context ac = { };
> + bool cold = ((gfp_mask & __GFP_COLD) != 0);
> +
> + /* If there are already pages on the list, don't bother */
> + if (!list_empty(alloc_list))
> + return 0;
> +
> + /* Only handle bulk allocation of order-0 */
> + if (order)
> + goto failed;
> +
> + gfp_mask &= gfp_allowed_mask;
> + if (!prepare_alloc_pages(gfp_mask, order, zonelist, nodemask, &ac, &alloc_mask, &alloc_flags))
> + return 0;
> +
> + finalise_ac(gfp_mask, order, &ac);
> + if (!ac.preferred_zoneref)
> + return 0;
> +
> + /*
> + * Only attempt a batch allocation if watermarks on the preferred zone
> + * are safe.
> + */
> + zone = ac.preferred_zoneref->zone;
> + if (!zone_watermark_fast(zone, order, zone->watermark[ALLOC_WMARK_HIGH] + nr_pages,
> + zonelist_zone_idx(ac.preferred_zoneref), alloc_flags))
> + goto failed;
> +
> + /* Attempt the batch allocation */
> + migratetype = ac.migratetype;
> +
> + local_irq_save(flags);
It would be a win if we could either use local_irq_{disable,enable} or
preempt_{disable,enable} here, by dictating it can only be used from
irq-safe context (like you did in patch 3).
> + pcp = &this_cpu_ptr(zone->pageset)->pcp;
> + pcp_list = &pcp->lists[migratetype];
> +
> + while (nr_pages) {
> + page = __rmqueue_pcplist(zone, order, gfp_mask, migratetype,
> + cold, pcp, pcp_list);
> + if (!page)
> + break;
> +
> + nr_pages--;
> + alloced++;
> + list_add(&page->lru, alloc_list);
> + }
> +
> + if (!alloced) {
> + local_irq_restore(flags);
> + preempt_enable();
The preempt_enable here looks wrong.
> + goto failed;
> + }
> +
> + __count_zid_vm_events(PGALLOC, zone_idx(zone), alloced);
> + zone_statistics(zone, zone, gfp_mask);
> +
> + local_irq_restore(flags);
> +
> + return alloced;
> +
> +failed:
> + page = __alloc_pages_nodemask(gfp_mask, order, zonelist, nodemask);
> + if (page) {
> + alloced++;
> + list_add(&page->lru, alloc_list);
> + }
> +
> + return alloced;
> +}
> +EXPORT_SYMBOL(__alloc_pages_bulk_nodemask);
> +
> +/*
> * Common helper functions.
> */
> unsigned long __get_free_pages(gfp_t gfp_mask, unsigned int order)
--
Best regards,
Jesper Dangaard Brouer
MSc.CS, Principal Kernel Engineer at Red Hat
LinkedIn: http://www.linkedin.com/in/brouer
^ permalink raw reply [flat|nested] 26+ messages in thread* Re: [PATCH 4/4] mm, page_alloc: Add a bulk page allocator
@ 2017-01-04 13:48 ` Jesper Dangaard Brouer
0 siblings, 0 replies; 26+ messages in thread
From: Jesper Dangaard Brouer @ 2017-01-04 13:48 UTC (permalink / raw)
To: Mel Gorman; +Cc: Linux Kernel, Linux-MM, brouer
On Wed, 4 Jan 2017 11:10:49 +0000
Mel Gorman <mgorman@techsingularity.net> wrote:
> This patch adds a new page allocator interface via alloc_pages_bulk,
> __alloc_pages_bulk and __alloc_pages_bulk_nodemask. A caller requests
> a number of pages to be allocated and added to a list. They can be
> freed in bulk using free_hot_cold_page_list.
>
> The API is not guaranteed to return the requested number of pages and
> may fail if the preferred allocation zone has limited free memory,
> the cpuset changes during the allocation or page debugging decides
> to fail an allocation. It's up to the caller to request more pages
> in batch if necessary.
I generally like it, thanks! :-)
> Signed-off-by: Mel Gorman <mgorman@techsingularity.net>
> ---
> include/linux/gfp.h | 23 ++++++++++++++
> mm/page_alloc.c | 92 +++++++++++++++++++++++++++++++++++++++++++++++++++++
> 2 files changed, 115 insertions(+)
>
> diff --git a/include/linux/gfp.h b/include/linux/gfp.h
> index 4175dca4ac39..1da3a9a48701 100644
> --- a/include/linux/gfp.h
> +++ b/include/linux/gfp.h
> @@ -433,6 +433,29 @@ __alloc_pages(gfp_t gfp_mask, unsigned int order,
> return __alloc_pages_nodemask(gfp_mask, order, zonelist, NULL);
> }
>
> +unsigned long
> +__alloc_pages_bulk_nodemask(gfp_t gfp_mask, unsigned int order,
> + struct zonelist *zonelist, nodemask_t *nodemask,
> + unsigned long nr_pages, struct list_head *alloc_list);
> +
> +static inline unsigned long
> +__alloc_pages_bulk(gfp_t gfp_mask, unsigned int order,
> + struct zonelist *zonelist, unsigned long nr_pages,
> + struct list_head *list)
> +{
> + return __alloc_pages_bulk_nodemask(gfp_mask, order, zonelist, NULL,
> + nr_pages, list);
> +}
> +
> +static inline unsigned long
> +alloc_pages_bulk(gfp_t gfp_mask, unsigned int order,
> + unsigned long nr_pages, struct list_head *list)
> +{
> + int nid = numa_mem_id();
> + return __alloc_pages_bulk(gfp_mask, order,
> + node_zonelist(nid, gfp_mask), nr_pages, list);
> +}
> +
> /*
> * Allocate pages, preferring the node given as nid. The node must be valid and
> * online. For more general interface, see alloc_pages_node().
> diff --git a/mm/page_alloc.c b/mm/page_alloc.c
> index 01b09f9da288..307ad4299dec 100644
> --- a/mm/page_alloc.c
> +++ b/mm/page_alloc.c
> @@ -3887,6 +3887,98 @@ __alloc_pages_nodemask(gfp_t gfp_mask, unsigned int order,
> EXPORT_SYMBOL(__alloc_pages_nodemask);
>
> /*
> + * This is a batched version of the page allocator that attempts to
> + * allocate nr_pages quickly from the preferred zone and add them to list.
> + * Note that there is no guarantee that nr_pages will be allocated although
> + * every effort will be made to allocate at least one. Unlike the core
> + * allocator, no special effort is made to recover from transient
> + * failures caused by changes in cpusets.
> + */
> +unsigned long
> +__alloc_pages_bulk_nodemask(gfp_t gfp_mask, unsigned int order,
> + struct zonelist *zonelist, nodemask_t *nodemask,
> + unsigned long nr_pages, struct list_head *alloc_list)
> +{
> + struct page *page;
> + unsigned long alloced = 0;
> + unsigned int alloc_flags = ALLOC_WMARK_LOW;
> + struct zone *zone;
> + struct per_cpu_pages *pcp;
> + struct list_head *pcp_list;
> + unsigned long flags;
> + int migratetype;
> + gfp_t alloc_mask = gfp_mask; /* The gfp_t that was actually used for allocation */
> + struct alloc_context ac = { };
> + bool cold = ((gfp_mask & __GFP_COLD) != 0);
> +
> + /* If there are already pages on the list, don't bother */
> + if (!list_empty(alloc_list))
> + return 0;
> +
> + /* Only handle bulk allocation of order-0 */
> + if (order)
> + goto failed;
> +
> + gfp_mask &= gfp_allowed_mask;
> + if (!prepare_alloc_pages(gfp_mask, order, zonelist, nodemask, &ac, &alloc_mask, &alloc_flags))
> + return 0;
> +
> + finalise_ac(gfp_mask, order, &ac);
> + if (!ac.preferred_zoneref)
> + return 0;
> +
> + /*
> + * Only attempt a batch allocation if watermarks on the preferred zone
> + * are safe.
> + */
> + zone = ac.preferred_zoneref->zone;
> + if (!zone_watermark_fast(zone, order, zone->watermark[ALLOC_WMARK_HIGH] + nr_pages,
> + zonelist_zone_idx(ac.preferred_zoneref), alloc_flags))
> + goto failed;
> +
> + /* Attempt the batch allocation */
> + migratetype = ac.migratetype;
> +
> + local_irq_save(flags);
It would be a win if we could either use local_irq_{disable,enable} or
preempt_{disable,enable} here, by dictating it can only be used from
irq-safe context (like you did in patch 3).
> + pcp = &this_cpu_ptr(zone->pageset)->pcp;
> + pcp_list = &pcp->lists[migratetype];
> +
> + while (nr_pages) {
> + page = __rmqueue_pcplist(zone, order, gfp_mask, migratetype,
> + cold, pcp, pcp_list);
> + if (!page)
> + break;
> +
> + nr_pages--;
> + alloced++;
> + list_add(&page->lru, alloc_list);
> + }
> +
> + if (!alloced) {
> + local_irq_restore(flags);
> + preempt_enable();
The preempt_enable here looks wrong.
> + goto failed;
> + }
> +
> + __count_zid_vm_events(PGALLOC, zone_idx(zone), alloced);
> + zone_statistics(zone, zone, gfp_mask);
> +
> + local_irq_restore(flags);
> +
> + return alloced;
> +
> +failed:
> + page = __alloc_pages_nodemask(gfp_mask, order, zonelist, nodemask);
> + if (page) {
> + alloced++;
> + list_add(&page->lru, alloc_list);
> + }
> +
> + return alloced;
> +}
> +EXPORT_SYMBOL(__alloc_pages_bulk_nodemask);
> +
> +/*
> * Common helper functions.
> */
> unsigned long __get_free_pages(gfp_t gfp_mask, unsigned int order)
--
Best regards,
Jesper Dangaard Brouer
MSc.CS, Principal Kernel Engineer at Red Hat
LinkedIn: http://www.linkedin.com/in/brouer
--
To unsubscribe, send a message with 'unsubscribe linux-mm' in
the body to majordomo@kvack.org. For more info on Linux MM,
see: http://www.linux-mm.org/ .
Don't email: <a href=mailto:"dont@kvack.org"> email@kvack.org </a>
^ permalink raw reply [flat|nested] 26+ messages in thread* Re: [PATCH 4/4] mm, page_alloc: Add a bulk page allocator
2017-01-04 13:48 ` Jesper Dangaard Brouer
@ 2017-01-04 14:03 ` Mel Gorman
-1 siblings, 0 replies; 26+ messages in thread
From: Mel Gorman @ 2017-01-04 14:03 UTC (permalink / raw)
To: Jesper Dangaard Brouer; +Cc: Linux Kernel, Linux-MM
On Wed, Jan 04, 2017 at 02:48:44PM +0100, Jesper Dangaard Brouer wrote:
> On Wed, 4 Jan 2017 11:10:49 +0000
> > The API is not guaranteed to return the requested number of pages and
> > may fail if the preferred allocation zone has limited free memory,
> > the cpuset changes during the allocation or page debugging decides
> > to fail an allocation. It's up to the caller to request more pages
> > in batch if necessary.
>
> I generally like it, thanks! :-)
>
No problem.
> > + /*
> > + * Only attempt a batch allocation if watermarks on the preferred zone
> > + * are safe.
> > + */
> > + zone = ac.preferred_zoneref->zone;
> > + if (!zone_watermark_fast(zone, order, zone->watermark[ALLOC_WMARK_HIGH] + nr_pages,
> > + zonelist_zone_idx(ac.preferred_zoneref), alloc_flags))
> > + goto failed;
> > +
> > + /* Attempt the batch allocation */
> > + migratetype = ac.migratetype;
> > +
> > + local_irq_save(flags);
>
> It would be a win if we could either use local_irq_{disable,enable} or
> preempt_{disable,enable} here, by dictating it can only be used from
> irq-safe context (like you did in patch 3).
>
This was a stupid mistake during a rebase. I should have removed all the
IRQ-disabling entirely and made it only usable from non-IRQ context to
keep the motivation of patch 3 in place. It was a botched rebase of the
patch on top of patch 3 that wasn't properly tested. It still illustrates
the general shape at least. For extra safety, I should force it to return
just a single page if called from interrupt context.
Is bulk allocation from IRQ context a requirement? If so, the motivation
for patch 3 disappears which is a pity but IRQ safety has a price. The
shape of V2 depends on the answer.
>
> > + pcp = &this_cpu_ptr(zone->pageset)->pcp;
> > + pcp_list = &pcp->lists[migratetype];
> > +
> > + while (nr_pages) {
> > + page = __rmqueue_pcplist(zone, order, gfp_mask, migratetype,
> > + cold, pcp, pcp_list);
> > + if (!page)
> > + break;
> > +
> > + nr_pages--;
> > + alloced++;
> > + list_add(&page->lru, alloc_list);
> > + }
> > +
> > + if (!alloced) {
> > + local_irq_restore(flags);
> > + preempt_enable();
>
> The preempt_enable here looks wrong.
>
It is because I screwed up the rebase.
--
Mel Gorman
SUSE Labs
^ permalink raw reply [flat|nested] 26+ messages in thread* Re: [PATCH 4/4] mm, page_alloc: Add a bulk page allocator
@ 2017-01-04 14:03 ` Mel Gorman
0 siblings, 0 replies; 26+ messages in thread
From: Mel Gorman @ 2017-01-04 14:03 UTC (permalink / raw)
To: Jesper Dangaard Brouer; +Cc: Linux Kernel, Linux-MM
On Wed, Jan 04, 2017 at 02:48:44PM +0100, Jesper Dangaard Brouer wrote:
> On Wed, 4 Jan 2017 11:10:49 +0000
> > The API is not guaranteed to return the requested number of pages and
> > may fail if the preferred allocation zone has limited free memory,
> > the cpuset changes during the allocation or page debugging decides
> > to fail an allocation. It's up to the caller to request more pages
> > in batch if necessary.
>
> I generally like it, thanks! :-)
>
No problem.
> > + /*
> > + * Only attempt a batch allocation if watermarks on the preferred zone
> > + * are safe.
> > + */
> > + zone = ac.preferred_zoneref->zone;
> > + if (!zone_watermark_fast(zone, order, zone->watermark[ALLOC_WMARK_HIGH] + nr_pages,
> > + zonelist_zone_idx(ac.preferred_zoneref), alloc_flags))
> > + goto failed;
> > +
> > + /* Attempt the batch allocation */
> > + migratetype = ac.migratetype;
> > +
> > + local_irq_save(flags);
>
> It would be a win if we could either use local_irq_{disable,enable} or
> preempt_{disable,enable} here, by dictating it can only be used from
> irq-safe context (like you did in patch 3).
>
This was a stupid mistake during a rebase. I should have removed all the
IRQ-disabling entirely and made it only usable from non-IRQ context to
keep the motivation of patch 3 in place. It was a botched rebase of the
patch on top of patch 3 that wasn't properly tested. It still illustrates
the general shape at least. For extra safety, I should force it to return
just a single page if called from interrupt context.
Is bulk allocation from IRQ context a requirement? If so, the motivation
for patch 3 disappears which is a pity but IRQ safety has a price. The
shape of V2 depends on the answer.
>
> > + pcp = &this_cpu_ptr(zone->pageset)->pcp;
> > + pcp_list = &pcp->lists[migratetype];
> > +
> > + while (nr_pages) {
> > + page = __rmqueue_pcplist(zone, order, gfp_mask, migratetype,
> > + cold, pcp, pcp_list);
> > + if (!page)
> > + break;
> > +
> > + nr_pages--;
> > + alloced++;
> > + list_add(&page->lru, alloc_list);
> > + }
> > +
> > + if (!alloced) {
> > + local_irq_restore(flags);
> > + preempt_enable();
>
> The preempt_enable here looks wrong.
>
It is because I screwed up the rebase.
--
Mel Gorman
SUSE Labs
--
To unsubscribe, send a message with 'unsubscribe linux-mm' in
the body to majordomo@kvack.org. For more info on Linux MM,
see: http://www.linux-mm.org/ .
Don't email: <a href=mailto:"dont@kvack.org"> email@kvack.org </a>
^ permalink raw reply [flat|nested] 26+ messages in thread