Re: [LKP] Re: [ext4] b1b4705d54: filebench.sum_bytes_mb/s -20.2% regression

[Xing Zhengjun]

ping...
The issue still exists in v5.6-rc7.

On 3/4/2020 4:15 PM, Xing Zhengjun wrote:
> Hi Matthew,
>
>  ÂWe test it in v5.6-rc4, the issue still exist, do you have time to 
> take a look at this? Thanks.
>
> On 1/8/2020 10:31 AM, Rong Chen wrote:
> > On 1/8/20 1:28 AM, Jan Kara wrote:
> > > 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:
> > > > > >
> > > > > > ÂÂÂÂdisk: 1HDD
> > > > > > ÂÂÂÂfs: ext4
> > > > > > ÂÂÂÂtest: fivestreamreaddirect.f
> > > > > > ÂÂÂÂcpufreq_governor: performance
> > > > > > ÂÂÂÂucode: 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:
> > >
> > > ÂÂÂÂÂ 58.30 ÂÂ 2%ÂÂÂÂ -20.2%ÂÂÂÂÂ 46.53ÂÂÂÂÂÂÂ 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).
> > > ÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂ Honza
> >
> > We're sorry for the misunderstanding, "-20.2%" means the change of 
> > filebench.sum_bytes_mb/s,
> > "regression" means the explanation of this change from LKP.
> >
> > Best Regards,
> > Rong Chen
> > _______________________________________________
> > LKP mailing list -- lkp@xxxxxxxxxxxx
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--
Zhengjun Xing