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. -- To unsubscribe from this list: send the line "unsubscribe linux-xfs" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
