* [PATCH 1/3] mm, page_alloc: Split buffered_rmqueue
2017-01-12 10:42 [PATCH 0/3] Use per-cpu allocator for !irq requests and prepare for a bulk allocator Mel Gorman
@ 2017-01-12 10:42 ` Mel Gorman
2017-01-12 15:44 ` Vlastimil Babka
2017-01-12 10:42 ` [PATCH 2/3] mm, page_alloc: Split alloc_pages_nodemask Mel Gorman
2017-01-12 10:43 ` [PATCH 3/3] mm, page_allocator: Only use per-cpu allocator for irq-safe requests Mel Gorman
2 siblings, 1 reply; 9+ messages in thread
From: Mel Gorman @ 2017-01-12 10:42 UTC (permalink / raw)
To: Andrew Morton
Cc: Linux Kernel, Linux-MM, Hillf Danton, Jesper Dangaard Brouer, 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>
Acked-by: Hillf Danton <hillf.zj@alibaba-inc.com>
---
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] 9+ messages in thread* Re: [PATCH 1/3] mm, page_alloc: Split buffered_rmqueue
2017-01-12 10:42 ` [PATCH 1/3] mm, page_alloc: Split buffered_rmqueue Mel Gorman
@ 2017-01-12 15:44 ` Vlastimil Babka
2017-01-12 17:21 ` Mel Gorman
0 siblings, 1 reply; 9+ messages in thread
From: Vlastimil Babka @ 2017-01-12 15:44 UTC (permalink / raw)
To: Mel Gorman, Andrew Morton
Cc: Linux Kernel, Linux-MM, Hillf Danton, Jesper Dangaard Brouer
On 01/12/2017 11:42 AM, Mel Gorman wrote:
> 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.
Strictly speaking, this will now skip VM_BUG_ON_PAGE(bad_range(...)) for order-0
allocations. Do we care?
> Signed-off-by: Mel Gorman <mgorman@techsingularity.net>
> Acked-by: Hillf Danton <hillf.zj@alibaba-inc.com>
> ---
> 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 */
^ Remove
> +static struct page *__rmqueue_pcplist(struct zone *zone, unsigned int order,
> + gfp_t gfp_flags, int migratetype, bool cold,
order and gfp_flags seem unused here
> + struct per_cpu_pages *pcp, struct list_head *list)
> +{
> + struct page *page;
^ permalink raw reply [flat|nested] 9+ messages in thread* Re: [PATCH 1/3] mm, page_alloc: Split buffered_rmqueue
2017-01-12 15:44 ` Vlastimil Babka
@ 2017-01-12 17:21 ` Mel Gorman
2017-01-13 13:27 ` Vlastimil Babka
0 siblings, 1 reply; 9+ messages in thread
From: Mel Gorman @ 2017-01-12 17:21 UTC (permalink / raw)
To: Vlastimil Babka
Cc: Andrew Morton, Linux Kernel, Linux-MM, Hillf Danton,
Jesper Dangaard Brouer
On Thu, Jan 12, 2017 at 04:44:20PM +0100, Vlastimil Babka wrote:
> On 01/12/2017 11:42 AM, Mel Gorman wrote:
> > 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.
>
> Strictly speaking, this will now skip VM_BUG_ON_PAGE(bad_range(...)) for
> order-0 allocations. Do we care?
>
Not very much but it still could be done.
> > Signed-off-by: Mel Gorman <mgorman@techsingularity.net>
> > Acked-by: Hillf Danton <hillf.zj@alibaba-inc.com>
> > ---
> > 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 */
>
> ^ Remove
>
> > +static struct page *__rmqueue_pcplist(struct zone *zone, unsigned int order,
> > + gfp_t gfp_flags, int migratetype, bool cold,
>
> order and gfp_flags seem unused here
>
This on top?
diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index d8798583eaf8..3b48e0315eb5 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -2610,10 +2610,10 @@ 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)
+/* Remove page from the per-cpu list, caller must protect the list */
+static struct page *__rmqueue_pcplist(struct zone *zone, int migratetype,
+ bool cold, struct per_cpu_pages *pcp,
+ struct list_head *list)
{
struct page *page;
@@ -2652,8 +2652,7 @@ static struct page *rmqueue_pcplist(struct zone *preferred_zone,
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);
+ page = __rmqueue_pcplist(zone, migratetype, cold, pcp, list);
if (page) {
__count_zid_vm_events(PGALLOC, page_zonenum(page), 1 << order);
zone_statistics(preferred_zone, zone, gfp_flags);
@@ -2674,9 +2673,11 @@ struct page *rmqueue(struct zone *preferred_zone,
unsigned long flags;
struct page *page;
- if (likely(order == 0))
- return rmqueue_pcplist(preferred_zone, zone, order,
+ if (likely(order == 0)) {
+ page = rmqueue_pcplist(preferred_zone, zone, order,
gfp_flags, migratetype);
+ goto out;
+ }
/*
* We most definitely don't want callers attempting to
@@ -2705,6 +2706,7 @@ struct page *rmqueue(struct zone *preferred_zone,
zone_statistics(preferred_zone, zone, gfp_flags);
local_irq_restore(flags);
+out:
VM_BUG_ON_PAGE(bad_range(zone, page), page);
return page;
--
Mel Gorman
SUSE Labs
^ permalink raw reply related [flat|nested] 9+ messages in thread* Re: [PATCH 1/3] mm, page_alloc: Split buffered_rmqueue
2017-01-12 17:21 ` Mel Gorman
@ 2017-01-13 13:27 ` Vlastimil Babka
0 siblings, 0 replies; 9+ messages in thread
From: Vlastimil Babka @ 2017-01-13 13:27 UTC (permalink / raw)
To: Mel Gorman
Cc: Andrew Morton, Linux Kernel, Linux-MM, Hillf Danton,
Jesper Dangaard Brouer
On 01/12/2017 06:21 PM, Mel Gorman wrote:
>
>> > Signed-off-by: Mel Gorman <mgorman@techsingularity.net>
>> > Acked-by: Hillf Danton <hillf.zj@alibaba-inc.com>
>> > ---
>> > 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 */
>>
>> ^ Remove
>>
>> > +static struct page *__rmqueue_pcplist(struct zone *zone, unsigned int order,
>> > + gfp_t gfp_flags, int migratetype, bool cold,
>>
>> order and gfp_flags seem unused here
>>
>
> This on top?
Yeah, thanks!
^ permalink raw reply [flat|nested] 9+ messages in thread
* [PATCH 2/3] mm, page_alloc: Split alloc_pages_nodemask
2017-01-12 10:42 [PATCH 0/3] Use per-cpu allocator for !irq requests and prepare for a bulk allocator Mel Gorman
2017-01-12 10:42 ` [PATCH 1/3] mm, page_alloc: Split buffered_rmqueue Mel Gorman
@ 2017-01-12 10:42 ` Mel Gorman
2017-01-12 10:43 ` [PATCH 3/3] mm, page_allocator: Only use per-cpu allocator for irq-safe requests Mel Gorman
2 siblings, 0 replies; 9+ messages in thread
From: Mel Gorman @ 2017-01-12 10:42 UTC (permalink / raw)
To: Andrew Morton
Cc: Linux Kernel, Linux-MM, Hillf Danton, Jesper Dangaard Brouer, 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>
Acked-by: Hillf Danton <hillf.zj@alibaba-inc.com>
---
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] 9+ messages in thread* [PATCH 3/3] mm, page_allocator: Only use per-cpu allocator for irq-safe requests
2017-01-12 10:42 [PATCH 0/3] Use per-cpu allocator for !irq requests and prepare for a bulk allocator Mel Gorman
2017-01-12 10:42 ` [PATCH 1/3] mm, page_alloc: Split buffered_rmqueue Mel Gorman
2017-01-12 10:42 ` [PATCH 2/3] mm, page_alloc: Split alloc_pages_nodemask Mel Gorman
@ 2017-01-12 10:43 ` Mel Gorman
2017-01-12 17:02 ` Vlastimil Babka
2 siblings, 1 reply; 9+ messages in thread
From: Mel Gorman @ 2017-01-12 10:43 UTC (permalink / raw)
To: Andrew Morton
Cc: Linux Kernel, Linux-MM, Hillf Danton, Jesper Dangaard Brouer, 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.
Jesper Dangaard Brouer independently tested
this with a separate microbenchmark from
https://github.com/netoptimizer/prototype-kernel/tree/master/kernel/mm/bench
Micro-benchmarked with [1] page_bench02:
modprobe page_bench02 page_order=0 run_flags=$((2#010)) loops=$((10**8)); \
rmmod page_bench02 ; dmesg --notime | tail -n 4
Compared to baseline: 213 cycles(tsc) 53.417 ns
- against this : 184 cycles(tsc) 46.056 ns
- Saving : -29 cycles
- Very close to expected 27 cycles saving [see below [2]]
Micro benchmarking via time_bench_sample[3], we get the cost of these
operations:
time_bench: Type:for_loop Per elem: 0 cycles(tsc) 0.232 ns (step:0)
time_bench: Type:spin_lock_unlock Per elem: 33 cycles(tsc) 8.334 ns (step:0)
time_bench: Type:spin_lock_unlock_irqsave Per elem: 62 cycles(tsc) 15.607 ns (step:0)
time_bench: Type:irqsave_before_lock Per elem: 57 cycles(tsc) 14.344 ns (step:0)
time_bench: Type:spin_lock_unlock_irq Per elem: 34 cycles(tsc) 8.560 ns (step:0)
time_bench: Type:simple_irq_disable_before_lock Per elem: 37 cycles(tsc) 9.289 ns (step:0)
time_bench: Type:local_BH_disable_enable Per elem: 19 cycles(tsc) 4.920 ns (step:0)
time_bench: Type:local_IRQ_disable_enable Per elem: 7 cycles(tsc) 1.864 ns (step:0)
time_bench: Type:local_irq_save_restore Per elem: 38 cycles(tsc) 9.665 ns (step:0)
[Mel's patch removes a ^^^^^^^^^^^^^^^^] ^^^^^^^^^ expected saving - preempt cost
time_bench: Type:preempt_disable_enable Per elem: 11 cycles(tsc) 2.794 ns (step:0)
[adds a preempt ^^^^^^^^^^^^^^^^^^^^^^] ^^^^^^^^^ adds this cost
time_bench: Type:funcion_call_cost Per elem: 6 cycles(tsc) 1.689 ns (step:0)
time_bench: Type:func_ptr_call_cost Per elem: 11 cycles(tsc) 2.767 ns (step:0)
time_bench: Type:page_alloc_put Per elem: 211 cycles(tsc) 52.803 ns (step:0)
Thus, expected improvement is: 38-11 = 27 cycles.
Signed-off-by: Mel Gorman <mgorman@techsingularity.net>
Acked-by: Hillf Danton <hillf.zj@alibaba-inc.com>
Acked-by: Jesper Dangaard Brouer <brouer@redhat.com>
---
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..232cadbe9231 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_no_resched();
}
/*
@@ -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_no_resched();
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] 9+ messages in thread* Re: [PATCH 3/3] mm, page_allocator: Only use per-cpu allocator for irq-safe requests
2017-01-12 10:43 ` [PATCH 3/3] mm, page_allocator: Only use per-cpu allocator for irq-safe requests Mel Gorman
@ 2017-01-12 17:02 ` Vlastimil Babka
2017-01-13 10:18 ` Mel Gorman
0 siblings, 1 reply; 9+ messages in thread
From: Vlastimil Babka @ 2017-01-12 17:02 UTC (permalink / raw)
To: Mel Gorman, Andrew Morton
Cc: Linux Kernel, Linux-MM, Hillf Danton, Jesper Dangaard Brouer
On 01/12/2017 11:43 AM, Mel Gorman 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. 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
>
<snip nice results>
>
> Signed-off-by: Mel Gorman <mgorman@techsingularity.net>
> Acked-by: Hillf Danton <hillf.zj@alibaba-inc.com>
> Acked-by: Jesper Dangaard Brouer <brouer@redhat.com>
Very promising! But I have some worries. Should we put something like
VM_BUG_ON(in_interrupt()) into free_hot_cold_page() and rmqueue_pcplist() to
catch future potential misuses and also document this requirement? Also
free_hot_cold_page() has other call sites besides __free_pages() and I'm not
sure if those are all guaranteed to be !IRQ? E.g. free_hot_cold_page_list()
which is called by release_page() which uses irq-safe lock operations...
Smaller nit below:
> @@ -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);
AFAICS preempt_disable() is enough for using __count_vm_event(), no?
> @@ -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);
But if I'm wrong above, then this __count should be converted too?
> zone_statistics(preferred_zone, zone, gfp_flags);
> }
> - local_irq_restore(flags);
> + preempt_enable_no_resched();
> return page;
> }
>
^ permalink raw reply [flat|nested] 9+ messages in thread
* Re: [PATCH 3/3] mm, page_allocator: Only use per-cpu allocator for irq-safe requests
2017-01-12 17:02 ` Vlastimil Babka
@ 2017-01-13 10:18 ` Mel Gorman
0 siblings, 0 replies; 9+ messages in thread
From: Mel Gorman @ 2017-01-13 10:18 UTC (permalink / raw)
To: Vlastimil Babka
Cc: Andrew Morton, Linux Kernel, Linux-MM, Hillf Danton,
Jesper Dangaard Brouer
On Thu, Jan 12, 2017 at 06:02:38PM +0100, Vlastimil Babka wrote:
> > Signed-off-by: Mel Gorman <mgorman@techsingularity.net>
> > Acked-by: Hillf Danton <hillf.zj@alibaba-inc.com>
> > Acked-by: Jesper Dangaard Brouer <brouer@redhat.com>
>
> Very promising! But I have some worries. Should we put something like
> VM_BUG_ON(in_interrupt()) into free_hot_cold_page() and rmqueue_pcplist() to
> catch future potential misuses and also document this requirement? Also
> free_hot_cold_page() has other call sites besides __free_pages() and I'm not
> sure if those are all guaranteed to be !IRQ? E.g. free_hot_cold_page_list()
> which is called by release_page() which uses irq-safe lock operations...
>
They are not guaranteed to be !irq but the API is easier to call incorrectly
than it could be. I think the checks can be pushed further down without
excessive overhead.
> Smaller nit below:
>
> > @@ -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);
>
> AFAICS preempt_disable() is enough for using __count_vm_event(), no?
>
It is, I'll fix it.
Thanks.
--
Mel Gorman
SUSE Labs
^ permalink raw reply [flat|nested] 9+ messages in thread