From: Wu Fengguang <fengguang.wu@intel.com>
Date: Tue, 16 Jun 2009 22:31:19 +0000 (-0700)
Subject: readahead: make mmap_miss an unsigned int
X-Git-Tag: v2.6.31-rc1~299^2~177
X-Git-Url: http://git.openpandora.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=1ebf26a9b338534def47f307c6c8694b6dfc0a79;p=pandora-kernel.git

readahead: make mmap_miss an unsigned int

This makes the performance impact of possible mmap_miss wrap around to be
temporary and tolerable: i.e.  MMAP_LOTSAMISS=100 extra readarounds.

Otherwise if ever mmap_miss wraps around to negative, it takes INT_MAX
cache misses to bring it back to normal state.  During the time mmap
readaround will be _enabled_ for whatever wild random workload.  That's
almost permanent performance impact.

Signed-off-by: Wu Fengguang <fengguang.wu@intel.com>
Cc: Ying Han <yinghan@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
---

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