[Your email is full of wacky symbols and needs line wrapping at 72 columns] On Thu, Sep 07, 2017 at 06:22:22PM +0000, Lu, Qian wrote: > Recently we received a bug report in the XFS filesystem with > 'discard' option. I have been able to reproduce this issue. I used > XFS filesystem to format NVMe SSD and mounted with 'discard' > option. When I tried to delete the test fio files, the session > took long time. This issue is based on Linux 4.9 stable tree. I > have also repeated this test with Linux 4.13, 4.12, and we are > facing the same issue. Tests were repeated several times and it > was consistent. ..... > > # fio --name fio_test_file --direct=1 --rw=randwrite --bs=4k --size=5G --numjobs=8 --group_reporting > --> Interrupt with Ctrl+C > # time rm -rf fio_test_file.* > real 2m2.242s > user 0m0.000s > sys 0m25.524s 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. Cheers, Dave. -- Dave Chinner david@xxxxxxxxxxxxx -- 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
