Commit 1b76b02f authored May 11, 2012 by Hugh Dickins Committed by Linus Torvalds May 11, 2012

mm: raise MemFree by reverting percpu_pagelist_fraction to 0



Why is there less MemFree than there used to be?  It perturbed a test,
so I've just been bisecting linux-next, and now find the offender went
upstream yesterday.

Commit 93278814 "mm: fix division by 0 in percpu_pagelist_fraction()"
mistakenly initialized percpu_pagelist_fraction to the sysctl's minimum 8,
which leaves 1/8th of memory on percpu lists (on each cpu??); but most of
us expect it to be left unset at 0 (and it's not then used as a divisor).

  MemTotal: 8061476kB  8061476kB  8061476kB  8061476kB  8061476kB  8061476kB
  Repetitive test with percpu_pagelist_fraction 8:
  MemFree:  6948420kB  6237172kB  6949696kB  6840692kB  6949048kB  6862984kB
  Same test with percpu_pagelist_fraction back to 0:
  MemFree:  7945000kB  7944908kB  7948568kB  7949060kB  7948796kB  7948812kB

Signed-off-by: Hugh Dickins <hughd@google.com>
[ We really should fix the crazy sysctl interface too, but that's a
  separate thing - Linus ]
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

parent d60b9c16

mm/page_alloc.c

+1 −1

Original line number	Diff line number	Diff line
		@@ -105,7 +105,7 @@ unsigned long totalreserve_pages __read_mostly;
		*/
		unsigned long dirty_balance_reserve __read_mostly;

		int percpu_pagelist_fraction = 8;
		int percpu_pagelist_fraction;
		gfp_t gfp_allowed_mask __read_mostly = GFP_BOOT_MASK;

		#ifdef CONFIG_PM_SLEEP

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