On 2/28/12 10:08 PM, Dave Chinner wrote: > Also, I think you need to provide a block trace (output of > blktrace/blkparse for the rm -rf workloads) for both the XFS and > ext4 cases so we can see what discards are actually being issued and > how long they take to complete.... > I ran a quick test on a loopback device on 3.3.0-rc4. Loopback supports discards. I made 1G filesystems on loopback on ext4 & xfs, mounted with -o discard, cloned a git tree to them, and ran rm -rf; sync under blktrace. XFS took about 11 seconds, ext4 took about 1.7. (without trim, times were roughly the same - but discard/trim is probably quite fast on the looback file) Both files were reduced in disk usage about the same amount, so online discard was working for both: # du -h ext4_fsfile xfs_fsfile 497M ext4_fsfile 491M xfs_fsfile XFS issued many more discards than ext4: # blkparse xfs.trace | grep -w D | wc -l 40205 # blkparse ext4.trace | grep -w D | wc -l 123 XFS issued many small discards (4k/8 sectors) and a few larger ones: [sectors | # discards] 8 20079 16 6762 24 3627 32 2798 40 1439 ... 1840 1 7256 1 26720 1 ext4 issued far fewer discards, but in much larger chunks: 8 29 16 9 24 4 32 6 ... 35152 1 35248 1 53744 1 192320 1 261624 1 262144 1 So that could certainly explain the relative speed. -Eric _______________________________________________ xfs mailing list xfs@xxxxxxxxxxx http://oss.sgi.com/mailman/listinfo/xfs
