From: Jan Kara <jack@suse.cz>
To: "Theodore Y. Ts'o" <tytso@mit.edu>
Cc: Jan Kara <jack@suse.cz>,
kernel test robot <rong.a.chen@intel.com>,
Matthew Bobrowski <mbobrowski@mbobrowski.org>,
Ritesh Harjani <riteshh@linux.ibm.com>,
LKML <linux-kernel@vger.kernel.org>,
Linus Torvalds <torvalds@linux-foundation.org>,
lkp@lists.01.org
Subject: Re: [ext4] b1b4705d54: filebench.sum_bytes_mb/s -20.2% regression
Date: Tue, 7 Jan 2020 18:28:24 +0100 [thread overview]
Message-ID: <20200107172824.GK25547@quack2.suse.cz> (raw)
In-Reply-To: <20200107165708.GA3619@mit.edu>
On Tue 07-01-20 11:57:08, Theodore Y. Ts'o wrote:
> On Tue, Jan 07, 2020 at 02:41:06PM +0100, Jan Kara wrote:
> > Hello,
> >
> > On Tue 24-12-19 08:59:15, kernel test robot wrote:
> > > FYI, we noticed a -20.2% regression of filebench.sum_bytes_mb/s due to commit:
> > >
> > >
> > > commit: b1b4705d54abedfd69dcdf42779c521aa1e0fbd3 ("ext4: introduce direct I/O read using iomap infrastructure")
> > > https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git master
> > >
> > > in testcase: filebench
> > > on test machine: 8 threads Intel(R) Core(TM) i7-4770 CPU @ 3.40GHz with 8G memory
> > > with following parameters:
> > >
> > > disk: 1HDD
> > > fs: ext4
> > > test: fivestreamreaddirect.f
> > > cpufreq_governor: performance
> > > ucode: 0x27
> >
> > I was trying to reproduce this but I failed with my test VM. I had SATA SSD
> > as a backing store though so maybe that's what makes a difference. Maybe
> > the new code results in somewhat more seeks because the five threads which
> > compete in submitting sequential IO end up being more interleaved?
>
> A "-20.2% regression" should be read as a "20.2% performance
> improvement" is zero-day kernel speak.
Are you sure? I can see:
58.30 ± 2% -20.2% 46.53 filebench.sum_bytes_mb/s
which implies to me previously the throughput was 58 MB/s and after the
commit it was 46 MB/s?
Anyway, in my testing that commit made no difference in that benchmark
whasoever (getting around 97 MB/s for each thread before and after the
commit).
Honza
--
Jan Kara <jack@suse.com>
SUSE Labs, CR
next prev parent reply other threads:[~2020-01-07 17:28 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-12-24 0:59 [ext4] b1b4705d54: filebench.sum_bytes_mb/s -20.2% regression kernel test robot
2020-01-07 13:41 ` Jan Kara
2020-01-07 16:57 ` Theodore Y. Ts'o
2020-01-07 17:28 ` Jan Kara [this message]
2020-01-08 2:31 ` Rong Chen
2020-03-04 8:15 ` [LKP] " Xing Zhengjun
2020-03-25 5:50 ` Xing Zhengjun
2020-03-25 14:31 ` Jan Kara
2020-04-15 7:55 ` Xing Zhengjun
2020-04-15 8:39 ` Jan Kara
2020-04-16 5:48 ` Xing Zhengjun
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