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author | KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com> | 2009-05-01 00:08:51 +0200 |
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committer | Linus Torvalds <torvalds@linux-foundation.org> | 2009-05-03 00:36:10 +0200 |
commit | 00a62ce91e554198ef28234c91c36f850f5a3bc9 (patch) | |
tree | 367ef134219deef91903c3fa0eb108c13658f2c7 | |
parent | of: make of_(un)register_platform_driver common code (diff) | |
download | linux-00a62ce91e554198ef28234c91c36f850f5a3bc9.tar.xz linux-00a62ce91e554198ef28234c91c36f850f5a3bc9.zip |
mm: fix Committed_AS underflow on large NR_CPUS environment
The Committed_AS field can underflow in certain situations:
> # while true; do cat /proc/meminfo | grep _AS; sleep 1; done | uniq -c
> 1 Committed_AS: 18446744073709323392 kB
> 11 Committed_AS: 18446744073709455488 kB
> 6 Committed_AS: 35136 kB
> 5 Committed_AS: 18446744073709454400 kB
> 7 Committed_AS: 35904 kB
> 3 Committed_AS: 18446744073709453248 kB
> 2 Committed_AS: 34752 kB
> 9 Committed_AS: 18446744073709453248 kB
> 8 Committed_AS: 34752 kB
> 3 Committed_AS: 18446744073709320960 kB
> 7 Committed_AS: 18446744073709454080 kB
> 3 Committed_AS: 18446744073709320960 kB
> 5 Committed_AS: 18446744073709454080 kB
> 6 Committed_AS: 18446744073709320960 kB
Because NR_CPUS can be greater than 1000 and meminfo_proc_show() does
not check for underflow.
But NR_CPUS proportional isn't good calculation. In general,
possibility of lock contention is proportional to the number of online
cpus, not theorical maximum cpus (NR_CPUS).
The current kernel has generic percpu-counter stuff. using it is right
way. it makes code simplify and percpu_counter_read_positive() don't
make underflow issue.
Reported-by: Dave Hansen <dave@linux.vnet.ibm.com>
Signed-off-by: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Cc: Eric B Munson <ebmunson@us.ibm.com>
Cc: Mel Gorman <mel@csn.ul.ie>
Cc: Christoph Lameter <cl@linux-foundation.org>
Cc: <stable@kernel.org> [All kernel versions]
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
-rw-r--r-- | fs/proc/meminfo.c | 2 | ||||
-rw-r--r-- | include/linux/mman.h | 9 | ||||
-rw-r--r-- | mm/mmap.c | 12 | ||||
-rw-r--r-- | mm/nommu.c | 13 | ||||
-rw-r--r-- | mm/swap.c | 46 |
5 files changed, 17 insertions, 65 deletions
diff --git a/fs/proc/meminfo.c b/fs/proc/meminfo.c index 74ea974f5ca6..c6b0302af4c4 100644 --- a/fs/proc/meminfo.c +++ b/fs/proc/meminfo.c @@ -35,7 +35,7 @@ static int meminfo_proc_show(struct seq_file *m, void *v) #define K(x) ((x) << (PAGE_SHIFT - 10)) si_meminfo(&i); si_swapinfo(&i); - committed = atomic_long_read(&vm_committed_space); + committed = percpu_counter_read_positive(&vm_committed_as); allowed = ((totalram_pages - hugetlb_total_pages()) * sysctl_overcommit_ratio / 100) + total_swap_pages; diff --git a/include/linux/mman.h b/include/linux/mman.h index 30d1073bac3b..9872d6ca58ae 100644 --- a/include/linux/mman.h +++ b/include/linux/mman.h @@ -12,21 +12,18 @@ #ifdef __KERNEL__ #include <linux/mm.h> +#include <linux/percpu_counter.h> #include <asm/atomic.h> extern int sysctl_overcommit_memory; extern int sysctl_overcommit_ratio; -extern atomic_long_t vm_committed_space; +extern struct percpu_counter vm_committed_as; -#ifdef CONFIG_SMP -extern void vm_acct_memory(long pages); -#else static inline void vm_acct_memory(long pages) { - atomic_long_add(pages, &vm_committed_space); + percpu_counter_add(&vm_committed_as, pages); } -#endif static inline void vm_unacct_memory(long pages) { diff --git a/mm/mmap.c b/mm/mmap.c index 3303d1ba8e87..6b7b1a95944b 100644 --- a/mm/mmap.c +++ b/mm/mmap.c @@ -85,7 +85,7 @@ EXPORT_SYMBOL(vm_get_page_prot); int sysctl_overcommit_memory = OVERCOMMIT_GUESS; /* heuristic overcommit */ int sysctl_overcommit_ratio = 50; /* default is 50% */ int sysctl_max_map_count __read_mostly = DEFAULT_MAX_MAP_COUNT; -atomic_long_t vm_committed_space = ATOMIC_LONG_INIT(0); +struct percpu_counter vm_committed_as; /* * Check that a process has enough memory to allocate a new virtual @@ -179,11 +179,7 @@ int __vm_enough_memory(struct mm_struct *mm, long pages, int cap_sys_admin) if (mm) allowed -= mm->total_vm / 32; - /* - * cast `allowed' as a signed long because vm_committed_space - * sometimes has a negative value - */ - if (atomic_long_read(&vm_committed_space) < (long)allowed) + if (percpu_counter_read_positive(&vm_committed_as) < allowed) return 0; error: vm_unacct_memory(pages); @@ -2481,4 +2477,8 @@ void mm_drop_all_locks(struct mm_struct *mm) */ void __init mmap_init(void) { + int ret; + + ret = percpu_counter_init(&vm_committed_as, 0); + VM_BUG_ON(ret); } diff --git a/mm/nommu.c b/mm/nommu.c index 72eda4aee2cb..809998aa7b50 100644 --- a/mm/nommu.c +++ b/mm/nommu.c @@ -62,7 +62,7 @@ void *high_memory; struct page *mem_map; unsigned long max_mapnr; unsigned long num_physpages; -atomic_long_t vm_committed_space = ATOMIC_LONG_INIT(0); +struct percpu_counter vm_committed_as; 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; @@ -463,6 +463,10 @@ SYSCALL_DEFINE1(brk, unsigned long, brk) */ void __init mmap_init(void) { + int ret; + + ret = percpu_counter_init(&vm_committed_as, 0); + VM_BUG_ON(ret); vm_region_jar = KMEM_CACHE(vm_region, SLAB_PANIC); } @@ -1847,12 +1851,9 @@ int __vm_enough_memory(struct mm_struct *mm, long pages, int cap_sys_admin) if (mm) allowed -= mm->total_vm / 32; - /* - * cast `allowed' as a signed long because vm_committed_space - * sometimes has a negative value - */ - if (atomic_long_read(&vm_committed_space) < (long)allowed) + if (percpu_counter_read_positive(&vm_committed_as) < allowed) return 0; + error: vm_unacct_memory(pages); diff --git a/mm/swap.c b/mm/swap.c index bede23ce64ea..cb29ae5d33ab 100644 --- a/mm/swap.c +++ b/mm/swap.c @@ -491,49 +491,6 @@ unsigned pagevec_lookup_tag(struct pagevec *pvec, struct address_space *mapping, EXPORT_SYMBOL(pagevec_lookup_tag); -#ifdef CONFIG_SMP -/* - * We tolerate a little inaccuracy to avoid ping-ponging the counter between - * CPUs - */ -#define ACCT_THRESHOLD max(16, NR_CPUS * 2) - -static DEFINE_PER_CPU(long, committed_space); - -void vm_acct_memory(long pages) -{ - long *local; - - preempt_disable(); - local = &__get_cpu_var(committed_space); - *local += pages; - if (*local > ACCT_THRESHOLD || *local < -ACCT_THRESHOLD) { - atomic_long_add(*local, &vm_committed_space); - *local = 0; - } - preempt_enable(); -} - -#ifdef CONFIG_HOTPLUG_CPU - -/* Drop the CPU's cached committed space back into the central pool. */ -static int cpu_swap_callback(struct notifier_block *nfb, - unsigned long action, - void *hcpu) -{ - long *committed; - - committed = &per_cpu(committed_space, (long)hcpu); - if (action == CPU_DEAD || action == CPU_DEAD_FROZEN) { - atomic_long_add(*committed, &vm_committed_space); - *committed = 0; - drain_cpu_pagevecs((long)hcpu); - } - return NOTIFY_OK; -} -#endif /* CONFIG_HOTPLUG_CPU */ -#endif /* CONFIG_SMP */ - /* * Perform any setup for the swap system */ @@ -554,7 +511,4 @@ void __init swap_setup(void) * Right now other parts of the system means that we * _really_ don't want to cluster much more */ -#ifdef CONFIG_HOTPLUG_CPU - hotcpu_notifier(cpu_swap_callback, 0); -#endif } |