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Message-ID: <4729EEB2.9090406@redhat.com> Date: Thu, 01 Nov 2007 10:20:18 -0500 From: Eric Sandeen <sandeen@...hat.com> To: Alex Tomas <bzzz.tomas@...il.com> CC: Andreas Dilger <adilger@....COM>, ext4 development <linux-ext4@...r.kernel.org> Subject: Re: delalloc fragmenting files? Alex Tomas wrote: > please, try the patch attached. Looks quite a bit better: http://people.redhat.com/esandeen/seekwatcher/ext4-alex.png http://people.redhat.com/esandeen/seekwatcher/ext4-alex-ext4-dd-write.png http://people.redhat.com/esandeen/seekwatcher/ext4-alex-ext4-xfs-dd-write.png It is much less fragmented, although still not exactly the nice linear allocation I'd expect from a single threaded large write on a fresh fs... -Eric > thanks, Alex > > Eric Sandeen wrote: >> One thing that seems to be happening is that thanks to delalloc, a nice >> big request is coming in (only 1036 blocks of the 4096, not quite sure >> why), but then it gets into ext4_mb_normalize_request(), which finds the >> most blocks it can "preallocate" is 256, and chops down the request to >> 256 blocks. Shouldn't this preallocation be over & above what was asked >> for, vs. reducing the request? >> >> Ok, so, we get allocations in 256-block chunks... Why they don't all >> come out contiguous, I don't know yet... >> >> -Eric > - To unsubscribe from this list: send the line "unsubscribe linux-ext4" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
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