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Re: [PATCH 0/1] qcow2: Skip copy-on-write when allocating a zero cluster
From: |
Brian Foster |
Subject: |
Re: [PATCH 0/1] qcow2: Skip copy-on-write when allocating a zero cluster |
Date: |
Tue, 25 Aug 2020 15:47:24 -0400 |
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
>
- Re: [PATCH 0/1] qcow2: Skip copy-on-write when allocating a zero cluster, (continued)
- Re: [PATCH 0/1] qcow2: Skip copy-on-write when allocating a zero cluster, Brian Foster, 2020/08/19
- Re: [PATCH 0/1] qcow2: Skip copy-on-write when allocating a zero cluster, Alberto Garcia, 2020/08/20
- Re: [PATCH 0/1] qcow2: Skip copy-on-write when allocating a zero cluster, Dave Chinner, 2020/08/20
- Re: [PATCH 0/1] qcow2: Skip copy-on-write when allocating a zero cluster, Brian Foster, 2020/08/21
- Re: [PATCH 0/1] qcow2: Skip copy-on-write when allocating a zero cluster, Alberto Garcia, 2020/08/21
- Re: [PATCH 0/1] qcow2: Skip copy-on-write when allocating a zero cluster, Alberto Garcia, 2020/08/21
- Re: [PATCH 0/1] qcow2: Skip copy-on-write when allocating a zero cluster, Brian Foster, 2020/08/21
- Re: [PATCH 0/1] qcow2: Skip copy-on-write when allocating a zero cluster, Alberto Garcia, 2020/08/25
- Re: [PATCH 0/1] qcow2: Skip copy-on-write when allocating a zero cluster, Brian Foster, 2020/08/25
- Re: [PATCH 0/1] qcow2: Skip copy-on-write when allocating a zero cluster, Alberto Garcia, 2020/08/25
- Re: [PATCH 0/1] qcow2: Skip copy-on-write when allocating a zero cluster,
Brian Foster <=
- Re: [PATCH 0/1] qcow2: Skip copy-on-write when allocating a zero cluster, Alberto Garcia, 2020/08/26
- Re: [PATCH 0/1] qcow2: Skip copy-on-write when allocating a zero cluster, Brian Foster, 2020/08/27
- Re: [PATCH 0/1] qcow2: Skip copy-on-write when allocating a zero cluster, Dave Chinner, 2020/08/23
- Re: [PATCH 0/1] qcow2: Skip copy-on-write when allocating a zero cluster, Alberto Garcia, 2020/08/24
- Re: [PATCH 0/1] qcow2: Skip copy-on-write when allocating a zero cluster, Brian Foster, 2020/08/21
- Re: [PATCH 0/1] qcow2: Skip copy-on-write when allocating a zero cluster, Alberto Garcia, 2020/08/21
- Re: [PATCH 0/1] qcow2: Skip copy-on-write when allocating a zero cluster, Dave Chinner, 2020/08/23
- Re: [PATCH 0/1] qcow2: Skip copy-on-write when allocating a zero cluster, Alberto Garcia, 2020/08/21