From: Jan Kara <jack@suse.cz>
To: Xing Zhengjun <zhengjun.xing@linux.intel.com>
Cc: Jan Kara <jack@suse.cz>,
kernel test robot <oliver.sang@intel.com>,
Theodore Ts'o <tytso@mit.edu>,
LKML <linux-kernel@vger.kernel.org>,
lkp@lists.01.org, lkp@intel.com
Subject: Re: [LKP] [ext4] 05c2c00f37: aim7.jobs-per-min -11.8% regression
Date: Fri, 21 May 2021 11:27:30 +0200 [thread overview]
Message-ID: <20210521092730.GE18952@quack2.suse.cz> (raw)
In-Reply-To: <e9f776c4-1ade-42a6-54c4-7fe3442e2392@linux.intel.com>
On Fri 21-05-21 09:16:42, Xing Zhengjun wrote:
> Hi Jan,
>
> On 5/20/2021 5:51 PM, Jan Kara wrote:
> > Hello!
> >
> > On Thu 20-05-21 15:13:20, Xing Zhengjun wrote:
> > >
> > > Do you have time to look at this? The regression still existed in the
> > > latest Linux mainline v5.13-rc2.
> >
> > Thanks for verification and for the ping! I had a look into this and I
> > think the regression is caused by the changes in orphan handling. The load
> > runs multiple tasks all creating and deleting files. This generally
> > contends on the orphan locking with fast storage (which is your case
> > because you use ramdisk as a backing store AFAICT). And the changes I did
> > move superblock checksum computation under the orphan lock so the lock hold
> > times are now higher.
> >
> > Sadly it is not easy to move checksum update from under the orphan lock and
> > maintain checksum consistency since the checksum has to be recomputed
> > consistently with the changes of superblock state. But I have one idea how
> > we could maybe improve the situation. Can you check whether attached patch
> > recovers the regression? Because that's about how good it could get when we
> > are more careful when writing out superblock.
> >
> > Honza
> >
>
> I apply the patch based on v5.13-rc2 and test, it can not recover the
> regression and the regression became more serious(-45.7%).
OK, thanks for testing. So the orphan code is indeed the likely cause of
this regression but I probably did not guess correctly what is the
contention point there. Then I guess I need to reproduce and do more
digging why the contention happens...
Honza
>
> =========================================================================================
> tbox_group/testcase/rootfs/kconfig/compiler/disk/md/fs/test/load/cpufreq_governor/ucode:
>
> lkp-csl-2sp9/aim7/debian-10.4-x86_64-20200603.cgz/x86_64-rhel-8.3/gcc-9/4BRD_12G/RAID1/ext4/creat-clo/1000/performance/0x5003006
>
> commit:
> 4392fbc4bab57db3760f0fb61258cb7089b37665
> 05c2c00f3769abb9e323fcaca70d2de0b48af7ba
> v5.13-rc2
> 2a1eb1a2fc08daaaf76a5aa8ffa355b5a5013d86 (the test patch)
>
> 4392fbc4bab57db3 05c2c00f3769abb9e323fcaca70 v5.13-rc2
> 2a1eb1a2fc08daaaf76a5aa8ffa
> ---------------- --------------------------- ---------------------------
> ---------------------------
> %stddev %change %stddev %change %stddev %change
> %stddev
> \ | \ | \
> | \
> 13342 -11.8% 11771 ± 2% -14.2% 11450
> -45.7% 7240 ± 3% aim7.jobs-per-min
>
>
>
> --
> Zhengjun Xing
--
Jan Kara <jack@suse.com>
SUSE Labs, CR
next prev parent reply other threads:[~2021-05-21 9:28 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-02-27 12:08 [ext4] 05c2c00f37: aim7.jobs-per-min -11.8% regression kernel test robot
[not found] ` <a8947cee-11f5-8d59-a3ff-1c516276592e@linux.intel.com>
2021-05-20 9:51 ` [LKP] " Jan Kara
2021-05-21 1:16 ` Xing Zhengjun
2021-05-21 9:27 ` Jan Kara [this message]
2021-05-21 16:42 ` Theodore Y. Ts'o
2021-05-25 9:22 ` Jan Kara
2021-05-25 17:15 ` Theodore Ts'o
2021-05-31 16:57 ` Jan Kara
2021-06-03 16:10 ` Jan Kara
2021-09-03 5:28 ` Xing Zhengjun
2021-09-03 12:32 ` Theodore Ts'o
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