Messages in this thread | | | Date | Thu, 25 Feb 2010 10:52:28 -0500 | From | Rik van Riel <> | Subject | Re: [PATCH 06/15] readahead: replace ra->mmap_miss with ra->ra_flags |
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On 02/23/2010 10:10 PM, Wu Fengguang wrote: > Introduce a readahead flags field and embed the existing mmap_miss in it > (mainly to save space). > > It also changes the mmap_miss upper bound from LONG_MAX to 4096. > This is to help adapt properly for changing mmap access patterns. > > It will be possible to lose the flags in race conditions, however the > impact should be limited. For the race to happen, there must be two > threads sharing the same file descriptor to be in page fault or > readahead at the same time. > > Note that it has always been racy for "page faults" at the same time. > > And if ever the race happen, we'll lose one mmap_miss++ or mmap_miss--. > Which may change some concrete readahead behavior, but won't really > impact overall I/O performance. > > CC: Nick Piggin<npiggin@suse.de> > CC: Andi Kleen<andi@firstfloor.org> > CC: Steven Whitehouse<swhiteho@redhat.com> > Signed-off-by: Wu Fengguang<fengguang.wu@intel.com>
Acked-by: Rik van Riel <riel@redhat.com>
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