Re: [patch] mm, thp: fix mlock statistics
From: Hugh Dickins <hughd@google.com>
Date: 2012-09-28 01:33:12
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On Wed, 26 Sep 2012, David Rientjes wrote:
NR_MLOCK is only accounted in single page units: there's no logic to handle transparent hugepages. This patch checks the appropriate number of pages to adjust the statistics by so that the correct amount of memory is reflected. Currently: $ grep Mlocked /proc/meminfo Mlocked: 19636 kB #define MAP_SIZE (4 << 30) /* 4GB */ void *ptr = mmap(NULL, MAP_SIZE, PROT_READ | PROT_WRITE, MAP_PRIVATE | MAP_ANONYMOUS, 0, 0); mlock(ptr, MAP_SIZE); $ grep Mlocked /proc/meminfo Mlocked: 29844 kB munlock(ptr, MAP_SIZE); $ grep Mlocked /proc/meminfo Mlocked: 19636 kB And with this patch: $ grep Mlock /proc/meminfo Mlocked: 19636 kB mlock(ptr, MAP_SIZE); $ grep Mlock /proc/meminfo Mlocked: 4213664 kB munlock(ptr, MAP_SIZE); $ grep Mlock /proc/meminfo Mlocked: 19636 kB Reported-by: Hugh Dickens <hughd@google.com>
I do prefer Dickins :)
Signed-off-by: David Rientjes <rientjes@google.com>
Acked-by: Hugh Dickins <hughd@google.com> Yes, this now seems to be working nicely, thanks. I would have preferred you to omit the free_page_mlock() part, since that sets me wondering about what flags might be set to mean what at that point; but since it should never get there anyway, and we'll be removing it entirely from v3.7, never mind. (In doing that, I shall need to consider whether clear_page_mlock() then needs hpage_nr_pages, but your patch below is perfectly correct to omit it.) If I understand aright, in another (thp: avoid VM_BUG_ON) thread, Linus remarks that he's noticed this and your matching Unevictable patch (that I had thought too late for v3.6), and is hoping for Acks so that he can put them into v3.6 after all. So despite my earlier reluctance, please take this as an Ack on that one too (I was testing them together): it'll be odd if one of them goes to stable and the other not, but we can sort that out with GregKH later. Hugh
quoted hunk ↗ jump to hunk
--- mm/internal.h | 3 ++- mm/mlock.c | 6 ++++-- mm/page_alloc.c | 2 +- 3 files changed, 7 insertions(+), 4 deletions(-)diff --git a/mm/internal.h b/mm/internal.h --- a/mm/internal.h +++ b/mm/internal.h@@ -180,7 +180,8 @@ static inline int mlocked_vma_newpage(struct vm_area_struct *vma, return 0; if (!TestSetPageMlocked(page)) { - inc_zone_page_state(page, NR_MLOCK); + mod_zone_page_state(page_zone(page), NR_MLOCK, + hpage_nr_pages(page)); count_vm_event(UNEVICTABLE_PGMLOCKED); } return 1;diff --git a/mm/mlock.c b/mm/mlock.c --- a/mm/mlock.c +++ b/mm/mlock.c@@ -81,7 +81,8 @@ void mlock_vma_page(struct page *page) BUG_ON(!PageLocked(page)); if (!TestSetPageMlocked(page)) { - inc_zone_page_state(page, NR_MLOCK); + mod_zone_page_state(page_zone(page), NR_MLOCK, + hpage_nr_pages(page)); count_vm_event(UNEVICTABLE_PGMLOCKED); if (!isolate_lru_page(page)) putback_lru_page(page);@@ -108,7 +109,8 @@ void munlock_vma_page(struct page *page) BUG_ON(!PageLocked(page)); if (TestClearPageMlocked(page)) { - dec_zone_page_state(page, NR_MLOCK); + mod_zone_page_state(page_zone(page), NR_MLOCK, + -hpage_nr_pages(page)); if (!isolate_lru_page(page)) { int ret = SWAP_AGAIN;diff --git a/mm/page_alloc.c b/mm/page_alloc.c --- a/mm/page_alloc.c +++ b/mm/page_alloc.c@@ -604,7 +604,7 @@ out: */ static inline void free_page_mlock(struct page *page) { - __dec_zone_page_state(page, NR_MLOCK); + __mod_zone_page_state(page_zone(page), NR_MLOCK, -hpage_nr_pages(page)); __count_vm_event(UNEVICTABLE_MLOCKFREED); }
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