From: Mel Gorman <mel@csn.ul.ie>
Date: Sun, 6 May 2007 21:49:30 +0000 (-0700)
Subject: Do not disable interrupts when reading min_free_kbytes
X-Git-Tag: v2.6.22-rc1~973
X-Git-Url: http://git.openpandora.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=3b1d92c56514987010bb0201b5c71aeb633fc4f8;p=pandora-kernel.git

Do not disable interrupts when reading min_free_kbytes

The sysctl handler for min_free_kbytes calls setup_per_zone_pages_min() on
read or write.  This function iterates through every zone and calls
spin_lock_irqsave() on the zone LRU lock.  When reading min_free_kbytes,
this is a total waste of time that disables interrupts on the local
processor.  It might even be noticable machines with large numbers of zones
if a process started constantly reading min_free_kbytes.

This patch only calls setup_per_zone_pages_min() only on write. Tested on
an x86 laptop and it did the right thing.

Signed-off-by: Mel Gorman <mel@csn.ul.ie>
Acked-by: Christoph Lameter <clameter@engr.sgi.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
---

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