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| author | Andrew Shewmaker <agshew@gmail.com> | 2013-04-29 15:08:11 -0700 |
|---|---|---|
| committer | Linus Torvalds <torvalds@linux-foundation.org> | 2013-04-29 15:54:36 -0700 |
| commit | 4eeab4f5580d11bffedc697684b91b0bca0d5009 (patch) | |
| tree | 4e9a0c010d34e786df52225039a17aa38e9adf17 /mm/mmap.c | |
| parent | c9b1d0981fcce3d9976d7b7a56e4e0503bc610dd (diff) | |
| download | linux-4eeab4f5580d11bffedc697684b91b0bca0d5009.tar.gz linux-4eeab4f5580d11bffedc697684b91b0bca0d5009.tar.bz2 linux-4eeab4f5580d11bffedc697684b91b0bca0d5009.zip | |
mm: replace hardcoded 3% with admin_reserve_pages knob
Add an admin_reserve_kbytes knob to allow admins to change the hardcoded
memory reserve to something other than 3%, which may be multiple
gigabytes on large memory systems. Only about 8MB is necessary to
enable recovery in the default mode, and only a few hundred MB are
required even when overcommit is disabled.
This affects OVERCOMMIT_GUESS and OVERCOMMIT_NEVER.
admin_reserve_kbytes is initialized to min(3% free pages, 8MB)
I arrived at 8MB by summing the RSS of sshd or login, bash, and top.
Please see first patch in this series for full background, motivation,
testing, and full changelog.
[akpm@linux-foundation.org: coding-style fixes]
[akpm@linux-foundation.org: make init_admin_reserve() static]
Signed-off-by: Andrew Shewmaker <agshew@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'mm/mmap.c')
| -rw-r--r-- | mm/mmap.c | 30 |
1 files changed, 26 insertions, 4 deletions
diff --git a/mm/mmap.c b/mm/mmap.c index 80a965f35251..5485f18e6631 100644 --- a/mm/mmap.c +++ b/mm/mmap.c @@ -85,6 +85,7 @@ int sysctl_overcommit_memory __read_mostly = OVERCOMMIT_GUESS; /* heuristic ove int sysctl_overcommit_ratio __read_mostly = 50; /* default is 50% */ int sysctl_max_map_count __read_mostly = DEFAULT_MAX_MAP_COUNT; unsigned long sysctl_user_reserve_kbytes __read_mostly = 1UL << 17; /* 128MB */ +unsigned long sysctl_admin_reserve_kbytes __read_mostly = 1UL << 13; /* 8MB */ /* * Make sure vm_committed_as in one cacheline and not cacheline shared with * other variables. It can be updated by several CPUs frequently. @@ -164,10 +165,10 @@ int __vm_enough_memory(struct mm_struct *mm, long pages, int cap_sys_admin) free -= totalreserve_pages; /* - * Leave the last 3% for root + * Reserve some for root */ if (!cap_sys_admin) - free -= free / 32; + free -= sysctl_admin_reserve_kbytes >> (PAGE_SHIFT - 10); if (free > pages) return 0; @@ -178,10 +179,10 @@ int __vm_enough_memory(struct mm_struct *mm, long pages, int cap_sys_admin) allowed = (totalram_pages - hugetlb_total_pages()) * sysctl_overcommit_ratio / 100; /* - * Leave the last 3% for root + * Reserve some for root */ if (!cap_sys_admin) - allowed -= allowed / 32; + allowed -= sysctl_admin_reserve_kbytes >> (PAGE_SHIFT - 10); allowed += total_swap_pages; /* @@ -3119,3 +3120,24 @@ static int __meminit init_user_reserve(void) return 0; } module_init(init_user_reserve) + +/* + * Initialise sysctl_admin_reserve_kbytes. + * + * The purpose of sysctl_admin_reserve_kbytes is to allow the sys admin + * to log in and kill a memory hogging process. + * + * Systems with more than 256MB will reserve 8MB, enough to recover + * with sshd, bash, and top in OVERCOMMIT_GUESS. Smaller systems will + * only reserve 3% of free pages by default. + */ +static int __meminit init_admin_reserve(void) +{ + unsigned long free_kbytes; + + free_kbytes = global_page_state(NR_FREE_PAGES) << (PAGE_SHIFT - 10); + + sysctl_admin_reserve_kbytes = min(free_kbytes / 32, 1UL << 13); + return 0; +} +module_init(init_admin_reserve) |