From 49f0ce5f92321cdcf741e35f385669a421013cb7 Mon Sep 17 00:00:00 2001 From: Jerome Marchand Date: Tue, 21 Jan 2014 15:49:14 -0800 Subject: [PATCH] mm: add overcommit_kbytes sysctl variable Some applications that run on HPC clusters are designed around the availability of RAM and the overcommit ratio is fine tuned to get the maximum usage of memory without swapping. With growing memory, the 1%-of-all-RAM grain provided by overcommit_ratio has become too coarse for these workload (on a 2TB machine it represents no less than 20GB). This patch adds the new overcommit_kbytes sysctl variable that allow a much finer grain. [akpm@linux-foundation.org: coding-style fixes] [akpm@linux-foundation.org: fix nommu build] Signed-off-by: Jerome Marchand Cc: Dave Hansen Cc: Alan Cox Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- Documentation/sysctl/vm.txt | 12 +++++++++ Documentation/vm/overcommit-accounting | 7 ++--- include/linux/mm.h | 9 +++++++ include/linux/mman.h | 1 + kernel/sysctl.c | 11 +++++--- mm/mmap.c | 1 + mm/nommu.c | 1 + mm/util.c | 36 ++++++++++++++++++++++++-- 8 files changed, 70 insertions(+), 8 deletions(-) diff --git a/Documentation/sysctl/vm.txt b/Documentation/sysctl/vm.txt index 1fbd4eb7b64a..9f5481bdc5a4 100644 --- a/Documentation/sysctl/vm.txt +++ b/Documentation/sysctl/vm.txt @@ -47,6 +47,7 @@ Currently, these files are in /proc/sys/vm: - numa_zonelist_order - oom_dump_tasks - oom_kill_allocating_task +- overcommit_kbytes - overcommit_memory - overcommit_ratio - page-cluster @@ -574,6 +575,17 @@ The default value is 0. ============================================================== +overcommit_kbytes: + +When overcommit_memory is set to 2, the committed address space is not +permitted to exceed swap plus this amount of physical RAM. See below. + +Note: overcommit_kbytes is the counterpart of overcommit_ratio. Only one +of them may be specified at a time. Setting one disables the other (which +then appears as 0 when read). + +============================================================== + overcommit_memory: This value contains a flag that enables memory overcommitment. diff --git a/Documentation/vm/overcommit-accounting b/Documentation/vm/overcommit-accounting index 8eaa2fc4b8fa..cbfaaa674118 100644 --- a/Documentation/vm/overcommit-accounting +++ b/Documentation/vm/overcommit-accounting @@ -14,8 +14,8 @@ The Linux kernel supports the following overcommit handling modes 2 - Don't overcommit. The total address space commit for the system is not permitted to exceed swap + a - configurable percentage (default is 50) of physical RAM. - Depending on the percentage you use, in most situations + configurable amount (default is 50%) of physical RAM. + Depending on the amount you use, in most situations this means a process will not be killed while accessing pages but will receive errors on memory allocation as appropriate. @@ -26,7 +26,8 @@ The Linux kernel supports the following overcommit handling modes The overcommit policy is set via the sysctl `vm.overcommit_memory'. -The overcommit percentage is set via `vm.overcommit_ratio'. +The overcommit amount can be set via `vm.overcommit_ratio' (percentage) +or `vm.overcommit_kbytes' (absolute value). The current overcommit limit and amount committed are viewable in /proc/meminfo as CommitLimit and Committed_AS respectively. diff --git a/include/linux/mm.h b/include/linux/mm.h index 4c0c01afc19b..a512dd836931 100644 --- a/include/linux/mm.h +++ b/include/linux/mm.h @@ -57,6 +57,15 @@ extern int sysctl_legacy_va_layout; extern unsigned long sysctl_user_reserve_kbytes; extern unsigned long sysctl_admin_reserve_kbytes; +extern int sysctl_overcommit_memory; +extern int sysctl_overcommit_ratio; +extern unsigned long sysctl_overcommit_kbytes; + +extern int overcommit_ratio_handler(struct ctl_table *, int, void __user *, + size_t *, loff_t *); +extern int overcommit_kbytes_handler(struct ctl_table *, int, void __user *, + size_t *, loff_t *); + #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/include/linux/mman.h b/include/linux/mman.h index 7f7f8dae4b1d..16373c8f5f57 100644 --- a/include/linux/mman.h +++ b/include/linux/mman.h @@ -9,6 +9,7 @@ extern int sysctl_overcommit_memory; extern int sysctl_overcommit_ratio; +extern unsigned long sysctl_overcommit_kbytes; extern struct percpu_counter vm_committed_as; #ifdef CONFIG_SMP diff --git a/kernel/sysctl.c b/kernel/sysctl.c index c8da99f905cf..332cefcdb04b 100644 --- a/kernel/sysctl.c +++ b/kernel/sysctl.c @@ -95,8 +95,6 @@ #if defined(CONFIG_SYSCTL) /* External variables not in a header file. */ -extern int sysctl_overcommit_memory; -extern int sysctl_overcommit_ratio; extern int max_threads; extern int suid_dumpable; #ifdef CONFIG_COREDUMP @@ -1121,7 +1119,14 @@ static struct ctl_table vm_table[] = { .data = &sysctl_overcommit_ratio, .maxlen = sizeof(sysctl_overcommit_ratio), .mode = 0644, - .proc_handler = proc_dointvec, + .proc_handler = overcommit_ratio_handler, + }, + { + .procname = "overcommit_kbytes", + .data = &sysctl_overcommit_kbytes, + .maxlen = sizeof(sysctl_overcommit_kbytes), + .mode = 0644, + .proc_handler = overcommit_kbytes_handler, }, { .procname = "page-cluster", diff --git a/mm/mmap.c b/mm/mmap.c index 834b2d785f1e..39552de6e1db 100644 --- a/mm/mmap.c +++ b/mm/mmap.c @@ -86,6 +86,7 @@ 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% */ +unsigned long sysctl_overcommit_kbytes __read_mostly; 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 */ diff --git a/mm/nommu.c b/mm/nommu.c index fec093adad9c..8740213b1647 100644 --- a/mm/nommu.c +++ b/mm/nommu.c @@ -60,6 +60,7 @@ unsigned long highest_memmap_pfn; struct percpu_counter vm_committed_as; int sysctl_overcommit_memory = OVERCOMMIT_GUESS; /* heuristic overcommit */ int sysctl_overcommit_ratio = 50; /* default is 50% */ +unsigned long sysctl_overcommit_kbytes __read_mostly; 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 */ diff --git a/mm/util.c b/mm/util.c index 808f375648e7..a24aa22f2473 100644 --- a/mm/util.c +++ b/mm/util.c @@ -404,13 +404,45 @@ struct address_space *page_mapping(struct page *page) return mapping; } +int overcommit_ratio_handler(struct ctl_table *table, int write, + void __user *buffer, size_t *lenp, + loff_t *ppos) +{ + int ret; + + ret = proc_dointvec(table, write, buffer, lenp, ppos); + if (ret == 0 && write) + sysctl_overcommit_kbytes = 0; + return ret; +} + +int overcommit_kbytes_handler(struct ctl_table *table, int write, + void __user *buffer, size_t *lenp, + loff_t *ppos) +{ + int ret; + + ret = proc_doulongvec_minmax(table, write, buffer, lenp, ppos); + if (ret == 0 && write) + sysctl_overcommit_ratio = 0; + return ret; +} + /* * Committed memory limit enforced when OVERCOMMIT_NEVER policy is used */ unsigned long vm_commit_limit(void) { - return ((totalram_pages - hugetlb_total_pages()) - * sysctl_overcommit_ratio / 100) + total_swap_pages; + unsigned long allowed; + + if (sysctl_overcommit_kbytes) + allowed = sysctl_overcommit_kbytes >> (PAGE_SHIFT - 10); + else + allowed = ((totalram_pages - hugetlb_total_pages()) + * sysctl_overcommit_ratio / 100); + allowed += total_swap_pages; + + return allowed; } -- GitLab