forked from luck/tmp_suning_uos_patched
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>
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@ -18,6 +18,7 @@ files can be found in mm/swap.c.
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Currently, these files are in /proc/sys/vm:
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- admin_reserve_kbytes
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- block_dump
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- compact_memory
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- dirty_background_bytes
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@ -59,6 +60,35 @@ Currently, these files are in /proc/sys/vm:
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==============================================================
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admin_reserve_kbytes
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The amount of free memory in the system that should be reserved for users
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with the capability cap_sys_admin.
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admin_reserve_kbytes defaults to min(3% of free pages, 8MB)
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That should provide enough for the admin to log in and kill a process,
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if necessary, under the default overcommit 'guess' mode.
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Systems running under overcommit 'never' should increase this to account
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for the full Virtual Memory Size of programs used to recover. Otherwise,
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root may not be able to log in to recover the system.
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How do you calculate a minimum useful reserve?
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sshd or login + bash (or some other shell) + top (or ps, kill, etc.)
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For overcommit 'guess', we can sum resident set sizes (RSS).
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On x86_64 this is about 8MB.
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For overcommit 'never', we can take the max of their virtual sizes (VSZ)
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and add the sum of their RSS.
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On x86_64 this is about 128MB.
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Changing this takes effect whenever an application requests memory.
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==============================================================
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block_dump
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block_dump enables block I/O debugging when set to a nonzero value. More
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@ -45,6 +45,7 @@ extern int sysctl_legacy_va_layout;
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#include <asm/processor.h>
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extern unsigned long sysctl_user_reserve_kbytes;
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extern unsigned long sysctl_admin_reserve_kbytes;
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#define nth_page(page,n) pfn_to_page(page_to_pfn((page)) + (n))
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@ -1436,6 +1436,13 @@ static struct ctl_table vm_table[] = {
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.mode = 0644,
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.proc_handler = proc_doulongvec_minmax,
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},
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{
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.procname = "admin_reserve_kbytes",
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.data = &sysctl_admin_reserve_kbytes,
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.maxlen = sizeof(sysctl_admin_reserve_kbytes),
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.mode = 0644,
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.proc_handler = proc_doulongvec_minmax,
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},
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{ }
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};
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30
mm/mmap.c
30
mm/mmap.c
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@ -85,6 +85,7 @@ int sysctl_overcommit_memory __read_mostly = OVERCOMMIT_GUESS; /* heuristic ove
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int sysctl_overcommit_ratio __read_mostly = 50; /* default is 50% */
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int sysctl_max_map_count __read_mostly = DEFAULT_MAX_MAP_COUNT;
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unsigned long sysctl_user_reserve_kbytes __read_mostly = 1UL << 17; /* 128MB */
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unsigned long sysctl_admin_reserve_kbytes __read_mostly = 1UL << 13; /* 8MB */
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/*
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* Make sure vm_committed_as in one cacheline and not cacheline shared with
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* other variables. It can be updated by several CPUs frequently.
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@ -164,10 +165,10 @@ int __vm_enough_memory(struct mm_struct *mm, long pages, int cap_sys_admin)
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free -= totalreserve_pages;
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/*
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* Leave the last 3% for root
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* Reserve some for root
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*/
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if (!cap_sys_admin)
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free -= free / 32;
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free -= sysctl_admin_reserve_kbytes >> (PAGE_SHIFT - 10);
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if (free > pages)
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return 0;
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@ -178,10 +179,10 @@ int __vm_enough_memory(struct mm_struct *mm, long pages, int cap_sys_admin)
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allowed = (totalram_pages - hugetlb_total_pages())
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* sysctl_overcommit_ratio / 100;
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/*
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* Leave the last 3% for root
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* Reserve some for root
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*/
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if (!cap_sys_admin)
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allowed -= allowed / 32;
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allowed -= sysctl_admin_reserve_kbytes >> (PAGE_SHIFT - 10);
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allowed += total_swap_pages;
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/*
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@ -3119,3 +3120,24 @@ static int __meminit init_user_reserve(void)
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return 0;
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}
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module_init(init_user_reserve)
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/*
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* Initialise sysctl_admin_reserve_kbytes.
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*
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* The purpose of sysctl_admin_reserve_kbytes is to allow the sys admin
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* to log in and kill a memory hogging process.
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*
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* Systems with more than 256MB will reserve 8MB, enough to recover
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* with sshd, bash, and top in OVERCOMMIT_GUESS. Smaller systems will
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* only reserve 3% of free pages by default.
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*/
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static int __meminit init_admin_reserve(void)
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{
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unsigned long free_kbytes;
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free_kbytes = global_page_state(NR_FREE_PAGES) << (PAGE_SHIFT - 10);
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sysctl_admin_reserve_kbytes = min(free_kbytes / 32, 1UL << 13);
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return 0;
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}
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module_init(init_admin_reserve)
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30
mm/nommu.c
30
mm/nommu.c
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@ -64,6 +64,7 @@ int sysctl_overcommit_ratio = 50; /* default is 50% */
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int sysctl_max_map_count = DEFAULT_MAX_MAP_COUNT;
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int sysctl_nr_trim_pages = CONFIG_NOMMU_INITIAL_TRIM_EXCESS;
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unsigned long sysctl_user_reserve_kbytes __read_mostly = 1UL << 17; /* 128MB */
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unsigned long sysctl_admin_reserve_kbytes __read_mostly = 1UL << 13; /* 8MB */
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int heap_stack_gap = 0;
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atomic_long_t mmap_pages_allocated;
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@ -1939,10 +1940,10 @@ int __vm_enough_memory(struct mm_struct *mm, long pages, int cap_sys_admin)
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free -= totalreserve_pages;
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/*
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* Leave the last 3% for root
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* Reserve some for root
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*/
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if (!cap_sys_admin)
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free -= free / 32;
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free -= sysctl_admin_reserve_kbytes >> (PAGE_SHIFT - 10);
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if (free > pages)
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return 0;
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@ -1952,10 +1953,10 @@ int __vm_enough_memory(struct mm_struct *mm, long pages, int cap_sys_admin)
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allowed = totalram_pages * sysctl_overcommit_ratio / 100;
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/*
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* Leave the last 3% for root
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* Reserve some 3% for root
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*/
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if (!cap_sys_admin)
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allowed -= allowed / 32;
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allowed -= sysctl_admin_reserve_kbytes >> (PAGE_SHIFT - 10);
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allowed += total_swap_pages;
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/*
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@ -2147,3 +2148,24 @@ static int __meminit init_user_reserve(void)
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return 0;
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}
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module_init(init_user_reserve)
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/*
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* Initialise sysctl_admin_reserve_kbytes.
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*
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* The purpose of sysctl_admin_reserve_kbytes is to allow the sys admin
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* to log in and kill a memory hogging process.
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*
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* Systems with more than 256MB will reserve 8MB, enough to recover
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* with sshd, bash, and top in OVERCOMMIT_GUESS. Smaller systems will
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* only reserve 3% of free pages by default.
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*/
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static int __meminit init_admin_reserve(void)
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{
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unsigned long free_kbytes;
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free_kbytes = global_page_state(NR_FREE_PAGES) << (PAGE_SHIFT - 10);
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sysctl_admin_reserve_kbytes = min(free_kbytes / 32, 1UL << 13);
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return 0;
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}
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module_init(init_admin_reserve)
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