diff options
| -rw-r--r-- | Documentation/sysctl/vm.txt | 20 | ||||
| -rw-r--r-- | Documentation/vm/overcommit-accounting | 8 | ||||
| -rw-r--r-- | include/linux/mm.h | 2 | ||||
| -rw-r--r-- | kernel/sysctl.c | 7 | ||||
| -rw-r--r-- | mm/mmap.c | 35 | ||||
| -rw-r--r-- | mm/nommu.c | 35 |
6 files changed, 96 insertions, 11 deletions
diff --git a/Documentation/sysctl/vm.txt b/Documentation/sysctl/vm.txt index 078701fdbd4..f6989573835 100644 --- a/Documentation/sysctl/vm.txt +++ b/Documentation/sysctl/vm.txt @@ -53,6 +53,7 @@ Currently, these files are in /proc/sys/vm: - percpu_pagelist_fraction - stat_interval - swappiness +- user_reserve_kbytes - vfs_cache_pressure - zone_reclaim_mode @@ -542,6 +543,7 @@ memory until it actually runs out. When this flag is 2, the kernel uses a "never overcommit" policy that attempts to prevent any overcommit of memory. +Note that user_reserve_kbytes affects this policy. This feature can be very useful because there are a lot of programs that malloc() huge amounts of memory "just-in-case" @@ -645,6 +647,24 @@ The default value is 60. ============================================================== +- user_reserve_kbytes + +When overcommit_memory is set to 2, "never overommit" mode, reserve +min(3% of current process size, user_reserve_kbytes) of free memory. +This is intended to prevent a user from starting a single memory hogging +process, such that they cannot recover (kill the hog). + +user_reserve_kbytes defaults to min(3% of the current process size, 128MB). + +If this is reduced to zero, then the user will be allowed to allocate +all free memory with a single process, minus admin_reserve_kbytes. +Any subsequent attempts to execute a command will result in +"fork: Cannot allocate memory". + +Changing this takes effect whenever an application requests memory. + +============================================================== + vfs_cache_pressure ------------------ diff --git a/Documentation/vm/overcommit-accounting b/Documentation/vm/overcommit-accounting index 706d7ed9d8d..8eaa2fc4b8f 100644 --- a/Documentation/vm/overcommit-accounting +++ b/Documentation/vm/overcommit-accounting @@ -8,7 +8,9 @@ The Linux kernel supports the following overcommit handling modes default. 1 - Always overcommit. Appropriate for some scientific - applications. + applications. Classic example is code using sparse arrays + and just relying on the virtual memory consisting almost + entirely of zero pages. 2 - Don't overcommit. The total address space commit for the system is not permitted to exceed swap + a @@ -18,6 +20,10 @@ The Linux kernel supports the following overcommit handling modes pages but will receive errors on memory allocation as appropriate. + Useful for applications that want to guarantee their + memory allocations will be available in the future + without having to initialize every page. + The overcommit policy is set via the sysctl `vm.overcommit_memory'. The overcommit percentage is set via `vm.overcommit_ratio'. diff --git a/include/linux/mm.h b/include/linux/mm.h index 7aa11a6736e..43cfaabbde4 100644 --- a/include/linux/mm.h +++ b/include/linux/mm.h @@ -44,6 +44,8 @@ extern int sysctl_legacy_va_layout; #include <asm/pgtable.h> #include <asm/processor.h> +extern unsigned long sysctl_user_reserve_kbytes; + #define nth_page(page,n) pfn_to_page(page_to_pfn((page)) + (n)) /* to align the pointer to the (next) page boundary */ diff --git a/kernel/sysctl.c b/kernel/sysctl.c index 3dadde52253..6daabb72bdb 100644 --- a/kernel/sysctl.c +++ b/kernel/sysctl.c @@ -1429,6 +1429,13 @@ static struct ctl_table vm_table[] = { .extra2 = &one, }, #endif + { + .procname = "user_reserve_kbytes", + .data = &sysctl_user_reserve_kbytes, + .maxlen = sizeof(sysctl_user_reserve_kbytes), + .mode = 0644, + .proc_handler = proc_doulongvec_minmax, + }, { } }; diff --git a/mm/mmap.c b/mm/mmap.c index 081e6da8e1a..80a965f3525 100644 --- a/mm/mmap.c +++ b/mm/mmap.c @@ -84,6 +84,7 @@ EXPORT_SYMBOL(vm_get_page_prot); int sysctl_overcommit_memory __read_mostly = OVERCOMMIT_GUESS; /* heuristic overcommit */ 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 */ /* * Make sure vm_committed_as in one cacheline and not cacheline shared with * other variables. It can be updated by several CPUs frequently. @@ -122,7 +123,7 @@ EXPORT_SYMBOL_GPL(vm_memory_committed); */ int __vm_enough_memory(struct mm_struct *mm, long pages, int cap_sys_admin) { - unsigned long free, allowed; + unsigned long free, allowed, reserve; vm_acct_memory(pages); @@ -183,10 +184,13 @@ int __vm_enough_memory(struct mm_struct *mm, long pages, int cap_sys_admin) allowed -= allowed / 32; allowed += total_swap_pages; - /* Don't let a single process grow too big: - leave 3% of the size of this process for other processes */ - if (mm) - allowed -= mm->total_vm / 32; + /* + * Don't let a single process grow so big a user can't recover + */ + if (mm) { + reserve = sysctl_user_reserve_kbytes >> (PAGE_SHIFT - 10); + allowed -= min(mm->total_vm / 32, reserve); + } if (percpu_counter_read_positive(&vm_committed_as) < allowed) return 0; @@ -3094,3 +3098,24 @@ void __init mmap_init(void) ret = percpu_counter_init(&vm_committed_as, 0); VM_BUG_ON(ret); } + +/* + * Initialise sysctl_user_reserve_kbytes. + * + * This is intended to prevent a user from starting a single memory hogging + * process, such that they cannot recover (kill the hog) in OVERCOMMIT_NEVER + * mode. + * + * The default value is min(3% of free memory, 128MB) + * 128MB is enough to recover with sshd/login, bash, and top/kill. + */ +static int __meminit init_user_reserve(void) +{ + unsigned long free_kbytes; + + free_kbytes = global_page_state(NR_FREE_PAGES) << (PAGE_SHIFT - 10); + + sysctl_user_reserve_kbytes = min(free_kbytes / 32, 1UL << 17); + return 0; +} +module_init(init_user_reserve) diff --git a/mm/nommu.c b/mm/nommu.c index 2f1c75ed468..58e4a0a5125 100644 --- a/mm/nommu.c +++ b/mm/nommu.c @@ -63,6 +63,7 @@ int sysctl_overcommit_memory = OVERCOMMIT_GUESS; /* heuristic overcommit */ int sysctl_overcommit_ratio = 50; /* default is 50% */ 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 */ int heap_stack_gap = 0; atomic_long_t mmap_pages_allocated; @@ -1897,7 +1898,7 @@ EXPORT_SYMBOL(unmap_mapping_range); */ int __vm_enough_memory(struct mm_struct *mm, long pages, int cap_sys_admin) { - unsigned long free, allowed; + unsigned long free, allowed, reserve; vm_acct_memory(pages); @@ -1957,10 +1958,13 @@ int __vm_enough_memory(struct mm_struct *mm, long pages, int cap_sys_admin) allowed -= allowed / 32; allowed += total_swap_pages; - /* Don't let a single process grow too big: - leave 3% of the size of this process for other processes */ - if (mm) - allowed -= mm->total_vm / 32; + /* + * Don't let a single process grow so big a user can't recover + */ + if (mm) { + reserve = sysctl_user_reserve_kbytes >> (PAGE_SHIFT - 10); + allowed -= min(mm->total_vm / 32, reserve); + } if (percpu_counter_read_positive(&vm_committed_as) < allowed) return 0; @@ -2122,3 +2126,24 @@ int nommu_shrink_inode_mappings(struct inode *inode, size_t size, up_write(&nommu_region_sem); return 0; } + +/* + * Initialise sysctl_user_reserve_kbytes. + * + * This is intended to prevent a user from starting a single memory hogging + * process, such that they cannot recover (kill the hog) in OVERCOMMIT_NEVER + * mode. + * + * The default value is min(3% of free memory, 128MB) + * 128MB is enough to recover with sshd/login, bash, and top/kill. + */ +static int __meminit init_user_reserve(void) +{ + unsigned long free_kbytes; + + free_kbytes = global_page_state(NR_FREE_PAGES) << (PAGE_SHIFT - 10); + + sysctl_user_reserve_kbytes = min(free_kbytes / 32, 1UL << 17); + return 0; +} +module_init(init_user_reserve) |