Re: EXT4 is ~2X as slow as XFS (593MB/s vs 304MB/s) for writes?

[Justin Piszcz]

On Sat, 27 Feb 2010, Dmitry Monakhov wrote:

> Justin Piszcz <jpiszcz@xxxxxxxxxxxxxxx> writes:
>
> > Hello,
> >
> > Is it possible to 'optimize' ext4 so it is as fast as XFS for writes?
> > I see about half the performance as XFS for sequential writes.
> >
> > I have checked the doc and tried several options, a few of which are shown
> > below (I have also tried the commit/journal_async/etc options but none of
> > them get the write speeds anywhere near XFS)?
> >
> > Sure 'dd' is not a real benchmark, etc, etc, but with 10Gbps between 2
> > hosts I get 550MiB/s+ on reads from EXT4 but only 100-200MiB/s write.
> >
> > When it was XFS I used to get 400-600MiB/s for writes for the same RAID
> > volume.
> >
> > How do I 'speed' up ext4?  Is it possible?
> I don't know how to speedup, but i do know how to slowdown XFS :)
> Seems that you forget to call fsync at the end of file write
> In this case some data may reside in memory cache.
> Please add  "conv=fsync" or "conv=fdatasync" to the dd cmd.
> And redone your measurements.

Hi,

First with a sync added in the total time (still 2x as fast)

EXT3:
p63:~# mount /dev/md0 -o nobarrier,data=writeback /r1
p63:~# cd /r1
p63:/r1# /usr/bin/time bash -c 'dd if=/dev/zero of=file bs=1M count=10240; sync'
10240+0 records in
10240+0 records out
10737418240 bytes (11 GB) copied, 35.4163 s, 303 MB/s
0.02user 19.85system 0:36.97elapsed 53%CPU (0avgtext+0avgdata 7296maxresident)k
0inputs+0outputs (5major+1145minor)pagefaults 0swaps

XFS:
p63:/r1# /usr/bin/time bash -c 'dd if=/dev/zero of=file bs=1M count=10240; sync'
10240+0 records in
10240+0 records out
10737418240 bytes (11 GB) copied, 18.08 s, 594 MB/s
0.03user 16.15system 0:18.67elapsed 86%CPU (0avgtext+0avgdata 7312maxresident)k
0inputs+0outputs (5major+1147minor)pagefaults 0swaps
p63:/r1#

Per your request: conv=fsync & conv=fdatasync


XFS:
p63:/r1# /usr/bin/time bash -c 'dd if=/dev/zero of=file bs=1M conv=fsync count=10240'
10240+0 records in
10240+0 records out
10737418240 bytes (11 GB) copied, 18.2142 s, 590 MB/s
0.03user 16.05system 0:18.21elapsed 88%CPU (0avgtext+0avgdata 7312maxresident)k
0inputs+0outputs (0major+832minor)pagefaults 0swaps
p63:/r1#

EXT3:
p63:/r1# /usr/bin/time bash -c 'dd if=/dev/zero of=file bs=1M conv=fdatasync count=10240'
10240+0 records in
10240+0 records out
10737418240 bytes (11 GB) copied, 39.5562 s, 271 MB/s

XFS:
p63:/r1# /usr/bin/time bash -c 'dd if=/dev/zero of=file bs=1M conv=fdatasync count=10240'
10240+0 records in
10240+0 records out
10737418240 bytes (11 GB) copied, 18.513 s, 580 MB/s
0.03user 16.25system 0:18.51elapsed 87%CPU (0avgtext+0avgdata 7312maxresident)k
0inputs+0outputs (5major+828minor)pagefaults 0swaps
p63:/r1#

p63:/r1# /usr/bin/time bash -c 'dd if=/dev/zero of=file bs=1M conv=fsync count=10240'
10240+0 records in
10240+0 records out
10737418240 bytes (11 GB) copied, 39.7859 s, 270 MB/s
0.02user 24.20system 0:39.79elapsed 60%CPU (0avgtext+0avgdata 7328maxresident)k
0inputs+0outputs (5major+829minor)pagefaults 0swaps
p63:/r1#

It is still 2x as fast?
Is there some other option I am missing here or is this correct?

Justin.

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