* [RFC PATCH] mm: update highest_memmap_pfn based on exact pfn
@ 2018-11-28 8:36 Wei Yang
2018-11-28 23:00 ` Andrew Morton
0 siblings, 1 reply; 3+ messages in thread
From: Wei Yang @ 2018-11-28 8:36 UTC (permalink / raw)
To: hughd, akpm, pasha.tatashin, mgorman; +Cc: linux-mm, Wei Yang
When DEFERRED_STRUCT_PAGE_INIT is set, page struct will not be
initialized all at boot up. Some of them is postponed to defer stage.
While the global variable highest_memmap_pfn is still set to the highest
pfn at boot up, even some of them are not initialized.
This patch adjust this behavior by update highest_memmap_pfn with the
exact pfn during each iteration. Since each node has a defer thread,
introduce a spin lock to protect it.
Signed-off-by: Wei Yang <richard.weiyang@gmail.com>
---
mm/internal.h | 8 ++++++++
mm/memory.c | 1 +
mm/nommu.c | 1 +
mm/page_alloc.c | 9 ++++++---
4 files changed, 16 insertions(+), 3 deletions(-)
diff --git a/mm/internal.h b/mm/internal.h
index 6a57811ae47d..f9e19c7d9b0a 100644
--- a/mm/internal.h
+++ b/mm/internal.h
@@ -79,6 +79,14 @@ static inline void set_page_refcounted(struct page *page)
}
extern unsigned long highest_memmap_pfn;
+extern spinlock_t highest_memmap_pfn_lock;
+static inline void update_highest_memmap_pfn(unsigned long end_pfn)
+{
+ spin_lock(&highest_memmap_pfn_lock);
+ if (highest_memmap_pfn < end_pfn - 1)
+ highest_memmap_pfn = end_pfn - 1;
+ spin_unlock(&highest_memmap_pfn_lock);
+}
/*
* Maximum number of reclaim retries without progress before the OOM
diff --git a/mm/memory.c b/mm/memory.c
index 4ad2d293ddc2..0cf9b88b51b7 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -127,6 +127,7 @@ unsigned long zero_pfn __read_mostly;
EXPORT_SYMBOL(zero_pfn);
unsigned long highest_memmap_pfn __read_mostly;
+DEFINE_SPINLOCK(highest_memmap_pfn_lock);
/*
* CONFIG_MMU architectures set up ZERO_PAGE in their paging_init()
diff --git a/mm/nommu.c b/mm/nommu.c
index 749276beb109..610dc6e17ce5 100644
--- a/mm/nommu.c
+++ b/mm/nommu.c
@@ -48,6 +48,7 @@ struct page *mem_map;
unsigned long max_mapnr;
EXPORT_SYMBOL(max_mapnr);
unsigned long highest_memmap_pfn;
+static DEFINE_SPINLOCK(highest_memmap_pfn_lock);
int sysctl_nr_trim_pages = CONFIG_NOMMU_INITIAL_TRIM_EXCESS;
int heap_stack_gap = 0;
diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index ccc86df24f28..33bb339aaef8 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -1216,6 +1216,7 @@ static void __meminit init_reserved_page(unsigned long pfn)
break;
}
__init_single_page(pfn_to_page(pfn), pfn, zid, nid);
+ update_highest_memmap_pfn(pfn);
}
#else
static inline void init_reserved_page(unsigned long pfn)
@@ -1540,6 +1541,7 @@ static unsigned long __init deferred_init_pages(int nid, int zid,
__init_single_page(page, pfn, zid, nid);
nr_pages++;
}
+ update_highest_memmap_pfn(pfn);
return (nr_pages);
}
@@ -5491,9 +5493,6 @@ void __meminit memmap_init_zone(unsigned long size, int nid, unsigned long zone,
unsigned long pfn, end_pfn = start_pfn + size;
struct page *page;
- if (highest_memmap_pfn < end_pfn - 1)
- highest_memmap_pfn = end_pfn - 1;
-
#ifdef CONFIG_ZONE_DEVICE
/*
* Honor reservation requested by the driver for this ZONE_DEVICE
@@ -5550,6 +5549,8 @@ void __meminit memmap_init_zone(unsigned long size, int nid, unsigned long zone,
cond_resched();
}
}
+
+ update_highest_memmap_pfn(pfn);
}
#ifdef CONFIG_ZONE_DEVICE
@@ -5622,6 +5623,8 @@ void __ref memmap_init_zone_device(struct zone *zone,
}
}
+ update_highest_memmap_pfn(pfn);
+
pr_info("%s initialised, %lu pages in %ums\n", dev_name(pgmap->dev),
size, jiffies_to_msecs(jiffies - start));
}
--
2.15.1
^ permalink raw reply related [flat|nested] 3+ messages in thread
* Re: [RFC PATCH] mm: update highest_memmap_pfn based on exact pfn
2018-11-28 8:36 [RFC PATCH] mm: update highest_memmap_pfn based on exact pfn Wei Yang
@ 2018-11-28 23:00 ` Andrew Morton
2018-11-29 2:08 ` Wei Yang
0 siblings, 1 reply; 3+ messages in thread
From: Andrew Morton @ 2018-11-28 23:00 UTC (permalink / raw)
To: Wei Yang; +Cc: hughd, pasha.tatashin, mgorman, linux-mm
On Wed, 28 Nov 2018 16:36:34 +0800 Wei Yang <richard.weiyang@gmail.com> wrote:
> When DEFERRED_STRUCT_PAGE_INIT is set, page struct will not be
> initialized all at boot up. Some of them is postponed to defer stage.
> While the global variable highest_memmap_pfn is still set to the highest
> pfn at boot up, even some of them are not initialized.
>
> This patch adjust this behavior by update highest_memmap_pfn with the
> exact pfn during each iteration. Since each node has a defer thread,
> introduce a spin lock to protect it.
>
Does this solve any known problems? If so then I'm suspecting that
those problems go deeper than this.
Why use a spinlock rather than an atomic_long_t?
Perhaps this check should instead be built into pfn_valid()?
^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: [RFC PATCH] mm: update highest_memmap_pfn based on exact pfn
2018-11-28 23:00 ` Andrew Morton
@ 2018-11-29 2:08 ` Wei Yang
0 siblings, 0 replies; 3+ messages in thread
From: Wei Yang @ 2018-11-29 2:08 UTC (permalink / raw)
To: Andrew Morton; +Cc: Wei Yang, hughd, pasha.tatashin, mgorman, linux-mm
On Wed, Nov 28, 2018 at 03:00:52PM -0800, Andrew Morton wrote:
>On Wed, 28 Nov 2018 16:36:34 +0800 Wei Yang <richard.weiyang@gmail.com> wrote:
>
>> When DEFERRED_STRUCT_PAGE_INIT is set, page struct will not be
>> initialized all at boot up. Some of them is postponed to defer stage.
>> While the global variable highest_memmap_pfn is still set to the highest
>> pfn at boot up, even some of them are not initialized.
>>
>> This patch adjust this behavior by update highest_memmap_pfn with the
>> exact pfn during each iteration. Since each node has a defer thread,
>> introduce a spin lock to protect it.
>>
>
>Does this solve any known problems? If so then I'm suspecting that
>those problems go deeper than this.
Corrently I don't see any problem.
>
>Why use a spinlock rather than an atomic_long_t?
Sorry for my shortage in knowledge. I am not sure how to compare and
change a value atomicly. cmpxchg just could compare the exact value.
>
>Perhaps this check should instead be built into pfn_valid()?
I think the original commit 22b31eec63e5 ('badpage: vm_normal_page use
print_bad_pte') introduce highest_memmap_pfn to make pfn_valid()
cheaper.
Some definition of pfn_valid() is :
#define pfn_valid(pfn) ((pfn) < max_pfn)
Which doesn't care about the exact presented or memmap-ed page.
I am not for sure all pfn_valid() could leverage this. One thing for
sure is there are only two users of highest_memmap_pfn
* vm_normal_page_pmd
* _vm_normal_page
--
Wei Yang
Help you, Help me
^ permalink raw reply [flat|nested] 3+ messages in thread
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2018-11-28 8:36 [RFC PATCH] mm: update highest_memmap_pfn based on exact pfn Wei Yang
2018-11-28 23:00 ` Andrew Morton
2018-11-29 2:08 ` Wei Yang
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