Messages in this thread | | | Date | Tue, 22 Nov 2005 12:24:43 +0800 | From | Wu Fengguang <> | Subject | Re: [PATCH] properly account readahead file major faults |
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Hi,
On Mon, Nov 21, 2005 at 12:00:38PM -0200, Marcelo Tosatti wrote: > Hi, > > The fault accounting of filemap_dopage() is currently unable to account > for readahead pages as major faults.
Sorry, I don't know much about the definition of major/minor page faults. So I googled one that explains the old behavior:
--> Page Faults <-- These come in two varieties. Minor and Major faults. A Major fault results when an application tries to access a memory page that has been swapped out to disk. The page must be swapped back in. A Minor fault results when an application tries to access a memory page that is still in memory, but the physical location of which is not immediately known. The address must be looked up.
With the current accounting logic: - major faults reflect the times one has to wait for real I/O. - the more success read-ahead, the less major faults. - anyway, major+minor faults remain the same for the same benchmark.
With your patch: - major faults are expected to remain the same with whatever read-ahead. - but what's the new meaning of minor faults?
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