The patch titled Subject: mm: replace hardcoded 3% with admin_reserve_pages knob has been removed from the -mm tree. Its filename was mm-replace-hardcoded-3%-with-admin_reserve_pages-knob.patch This patch was dropped because it was merged into mainline or a subsystem tree ------------------------------------------------------ From: Andrew Shewmaker <agshew@xxxxxxxxx> Subject: 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@xxxxxxxxxxxxxxxxxxxx: coding-style fixes] [akpm@xxxxxxxxxxxxxxxxxxxx: make init_admin_reserve() static] Signed-off-by: Andrew Shewmaker <agshew@xxxxxxxxx> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> --- Documentation/sysctl/vm.txt | 30 ++++++++++++++++++++++++++++++ include/linux/mm.h | 1 + kernel/sysctl.c | 7 +++++++ mm/mmap.c | 30 ++++++++++++++++++++++++++---- mm/nommu.c | 30 ++++++++++++++++++++++++++---- 5 files changed, 90 insertions(+), 8 deletions(-) diff -puN Documentation/sysctl/vm.txt~mm-replace-hardcoded-3%-with-admin_reserve_pages-knob Documentation/sysctl/vm.txt --- a/Documentation/sysctl/vm.txt~mm-replace-hardcoded-3%-with-admin_reserve_pages-knob +++ a/Documentation/sysctl/vm.txt @@ -18,6 +18,7 @@ files can be found in mm/swap.c. Currently, these files are in /proc/sys/vm: +- admin_reserve_kbytes - block_dump - compact_memory - dirty_background_bytes @@ -59,6 +60,35 @@ Currently, these files are in /proc/sys/ ============================================================== +admin_reserve_kbytes + +The amount of free memory in the system that should be reserved for users +with the capability cap_sys_admin. + +admin_reserve_kbytes defaults to min(3% of free pages, 8MB) + +That should provide enough for the admin to log in and kill a process, +if necessary, under the default overcommit 'guess' mode. + +Systems running under overcommit 'never' should increase this to account +for the full Virtual Memory Size of programs used to recover. Otherwise, +root may not be able to log in to recover the system. + +How do you calculate a minimum useful reserve? + +sshd or login + bash (or some other shell) + top (or ps, kill, etc.) + +For overcommit 'guess', we can sum resident set sizes (RSS). +On x86_64 this is about 8MB. + +For overcommit 'never', we can take the max of their virtual sizes (VSZ) +and add the sum of their RSS. +On x86_64 this is about 128MB. + +Changing this takes effect whenever an application requests memory. + +============================================================== + block_dump block_dump enables block I/O debugging when set to a nonzero value. More diff -puN include/linux/mm.h~mm-replace-hardcoded-3%-with-admin_reserve_pages-knob include/linux/mm.h --- a/include/linux/mm.h~mm-replace-hardcoded-3%-with-admin_reserve_pages-knob +++ a/include/linux/mm.h @@ -45,6 +45,7 @@ extern int sysctl_legacy_va_layout; #include <asm/processor.h> extern unsigned long sysctl_user_reserve_kbytes; +extern unsigned long sysctl_admin_reserve_kbytes; #define nth_page(page,n) pfn_to_page(page_to_pfn((page)) + (n)) diff -puN kernel/sysctl.c~mm-replace-hardcoded-3%-with-admin_reserve_pages-knob kernel/sysctl.c --- a/kernel/sysctl.c~mm-replace-hardcoded-3%-with-admin_reserve_pages-knob +++ a/kernel/sysctl.c @@ -1436,6 +1436,13 @@ static struct ctl_table vm_table[] = { .mode = 0644, .proc_handler = proc_doulongvec_minmax, }, + { + .procname = "admin_reserve_kbytes", + .data = &sysctl_admin_reserve_kbytes, + .maxlen = sizeof(sysctl_admin_reserve_kbytes), + .mode = 0644, + .proc_handler = proc_doulongvec_minmax, + }, { } }; diff -puN mm/mmap.c~mm-replace-hardcoded-3%-with-admin_reserve_pages-knob mm/mmap.c --- a/mm/mmap.c~mm-replace-hardcoded-3%-with-admin_reserve_pages-knob +++ a/mm/mmap.c @@ -85,6 +85,7 @@ int sysctl_overcommit_memory __read_most 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 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 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(v 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) diff -puN mm/nommu.c~mm-replace-hardcoded-3%-with-admin_reserve_pages-knob mm/nommu.c --- a/mm/nommu.c~mm-replace-hardcoded-3%-with-admin_reserve_pages-knob +++ a/mm/nommu.c @@ -64,6 +64,7 @@ int sysctl_overcommit_ratio = 50; /* def int sysctl_max_map_count = DEFAULT_MAX_MAP_COUNT; int sysctl_nr_trim_pages = CONFIG_NOMMU_INITIAL_TRIM_EXCESS; unsigned long sysctl_user_reserve_kbytes __read_mostly = 1UL << 17; /* 128MB */ +unsigned long sysctl_admin_reserve_kbytes __read_mostly = 1UL << 13; /* 8MB */ int heap_stack_gap = 0; atomic_long_t mmap_pages_allocated; @@ -1939,10 +1940,10 @@ int __vm_enough_memory(struct mm_struct 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; @@ -1952,10 +1953,10 @@ int __vm_enough_memory(struct mm_struct allowed = totalram_pages * sysctl_overcommit_ratio / 100; /* - * Leave the last 3% for root + * Reserve some 3% for root */ if (!cap_sys_admin) - allowed -= allowed / 32; + allowed -= sysctl_admin_reserve_kbytes >> (PAGE_SHIFT - 10); allowed += total_swap_pages; /* @@ -2147,3 +2148,24 @@ static int __meminit init_user_reserve(v 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) _ Patches currently in -mm which might be from agshew@xxxxxxxxx are origin.patch -- To unsubscribe from this list: send the line "unsubscribe mm-commits" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html