Messages in this thread | | | Date | Fri, 8 Sep 2017 00:16:30 -0700 | From | Christoph Hellwig <> | Subject | Re: XFS mounted with 'discard' option - deleting fio test files slow |
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On Fri, Sep 08, 2017 at 09:34:02AM +1000, Dave Chinner wrote: > 4k random write with direct IO. 5GB file. Probably got a million 4k > extents in it. Which means XFS has sent a million tiny 4k discards > to the device. Run 'xfs_bmap -vvp fio_test_file.*' to confirm. > > Don't use "-o discard" if you care about performance.
And your device sucks :)
Some numbers here:
https://events.linuxfoundation.org/sites/events/files/slides/discard_0.pdf
Discard will cause extra work, and for worst case sceanarios lots of it. But some device handle that extra load very well.
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