On Tue, Aug 25, 2020 at 07:18:19PM +0200, Alberto Garcia wrote: > On Tue 25 Aug 2020 06:54:15 PM CEST, Brian Foster wrote: > > If I compare this 5m fio test between XFS and ext4 on a couple of my > > systems (with either no prealloc or full file prealloc), I end up seeing > > ext4 run slightly faster on my vm and XFS slightly faster on bare metal. > > Either way, I don't see that huge disparity where ext4 is 5-6 times > > faster than XFS. Can you describe the test, filesystem and storage in > > detail where you observe such a discrepancy? > > Here's the test: > > fio --filename=/path/to/file.raw --direct=1 --randrepeat=1 \ > --eta=always --ioengine=libaio --iodepth=32 --numjobs=1 \ > --name=test --size=25G --io_limit=25G --ramp_time=0 \ > --rw=randwrite --bs=4k --runtime=300 --time_based=1 > My fio fallocates the entire file by default with this command. Is that the intent of this particular test? I added --fallocate=none to my test runs to incorporate the allocation cost in the I/Os. > The size of the XFS filesystem is 126 GB and it's almost empty, here's > the xfs_info output: > > meta-data=/dev/vg/test isize=512 agcount=4, agsize=8248576 > blks > = sectsz=512 attr=2, projid32bit=1 > = crc=1 finobt=1, sparse=1, > rmapbt=0 > = reflink=0 > data = bsize=4096 blocks=32994304, imaxpct=25 > = sunit=0 swidth=0 blks > naming =version 2 bsize=4096 ascii-ci=0, ftype=1 > log =internal log bsize=4096 blocks=16110, version=2 > = sectsz=512 sunit=0 blks, lazy-count=1 > realtime =none extsz=4096 blocks=0, rtextents=0 > > The size of the ext4 filesystem is 99GB, of which 49GB are free (that > is, without the file used in this test). The filesystem uses 4KB > blocks, a 128M journal and these features: > > Filesystem revision #: 1 (dynamic) > Filesystem features: has_journal ext_attr resize_inode dir_index > filetype needs_recovery extent flex_bg > sparse_super large_file huge_file uninit_bg > dir_nlink extra_isize > Filesystem flags: signed_directory_hash > Default mount options: user_xattr acl > > In both cases I'm using LVM on top of LUKS and the hard drive is a > Samsung SSD 850 PRO 1TB. > > The Linux version is 4.19.132-1 from Debian. > Thanks. I don't have LUKS in the mix on my box, but I was running on a more recent kernel (Fedora 5.7.15-100). I threw v4.19 on the box and saw a bit more of a delta between XFS (~14k iops) and ext4 (~24k). The same test shows ~17k iops for XFS and ~19k iops for ext4 on v5.7. If I increase the size of the LVM volume from 126G to >1TB, ext4 runs at roughly the same rate and XFS closes the gap to around ~19k iops as well. I'm not sure what might have changed since v4.19, but care to see if this is still an issue on a more recent kernel? Brian > Berto >
