Messages in this thread | | | Date | Wed, 18 Apr 2012 09:57:10 -0500 | From | Eric Sandeen <> | Subject | Re: [RFC][PATCH 0/3] add FALLOC_FL_NO_HIDE_STALE flag in fallocate |
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On 4/17/12 11:59 PM, Andreas Dilger wrote:
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> Secondly, your test program is not doing random writes to disk, but > rather doing writes at 64kB intervals. There is logic in the > uninitialized extent handling that will write zeros to an entire > extent, rather than create many fragmented uninitialized extents. It > may be possible that you are zeroing out the entire file, and writing > 16x as much data as you expect. > > Cheers, Andreas
I don't think the testcase as written is triggering that behavior, though other similar testcases might. In this case the left-over uninit extents are large enough that they don't get zeroed:
File size of /mnt/scratch/test is 268435456 (65536 blocks, blocksize 4096) ext logical physical expected length flags 0 0 34816 1 1 1 34817 15 unwritten 2 16 34832 1 3 17 34833 15 unwritten 4 32 34848 1 5 33 34849 15 unwritten ...
Good guess though :)
-Eric
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