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authorKOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>2009-04-30 15:08:51 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2009-05-02 15:36:10 -0700
commit00a62ce91e554198ef28234c91c36f850f5a3bc9 (patch)
tree367ef134219deef91903c3fa0eb108c13658f2c7 /include
parent0763ed2355198cdef2f6a2098e9d52eb1fe4365d (diff)
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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>
Diffstat (limited to 'include')
-rw-r--r--include/linux/mman.h9
1 files changed, 3 insertions, 6 deletions
diff --git a/include/linux/mman.h b/include/linux/mman.h
index 30d1073bac3..9872d6ca58a 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)
{