Messages in this thread Patch in this message | | | From | Roman Gushchin <> | Subject | [PATCH] mm: don't account shared file pages in user_reserve_pages | Date | Thu, 29 Jan 2015 14:51:27 +0300 |
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Shared file pages are never accounted in memory overcommit code, so it isn't reasonable to count them in a code that limits the maximal size of a process in OVERCOMMIT_NONE mode.
If a process has few large file mappings, the consequent attempts to allocate anonymous memory may unexpectedly fail with -ENOMEM, while there is free memory and overcommit limit if significantly larger than the committed amount (as displayed in /proc/meminfo).
The problem is significantly smoothed by commit c9b1d0981fcc ("mm: limit growth of 3% hardcoded other user reserve"), which limits the impact of this check with 128Mb (tunable via sysctl), but it can still be a problem on small machines.
Signed-off-by: Roman Gushchin <klamm@yandex-team.ru> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: Andrew Shewmaker <agshew@gmail.com> Cc: Rik van Riel <riel@redhat.com> Cc: Konstantin Khlebnikov <khlebnikov@yandex-team.ru> --- mm/mmap.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/mm/mmap.c b/mm/mmap.c index 7f684d5..151fadf 100644 --- a/mm/mmap.c +++ b/mm/mmap.c @@ -220,7 +220,7 @@ int __vm_enough_memory(struct mm_struct *mm, long pages, int cap_sys_admin) */ if (mm) { reserve = sysctl_user_reserve_kbytes >> (PAGE_SHIFT - 10); - allowed -= min(mm->total_vm / 32, reserve); + allowed -= min((mm->total_vm - mm->shared_vm) / 32, reserve); } if (percpu_counter_read_positive(&vm_committed_as) < allowed) -- 2.1.0
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