linux-kernel - Re: [linus:master] [readahead] ab4443fe3c: vm-scalability.throughput -21.4% regression

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Date: Thu, 22 Feb 2024 12:50:32 +0100
From: Jan Kara <jack@...e.cz>
To: Oliver Sang <oliver.sang@...el.com>
Cc: Jan Kara <jack@...e.cz>, oe-lkp@...ts.linux.dev, lkp@...el.com,
	linux-kernel@...r.kernel.org,
	Andrew Morton <akpm@...ux-foundation.org>,
	Matthew Wilcox <willy@...radead.org>,
	Guo Xuenan <guoxuenan@...wei.com>, linux-fsdevel@...r.kernel.org,
	ying.huang@...el.com, feng.tang@...el.com, fengwei.yin@...el.com
Subject: Re: [linus:master] [readahead]  ab4443fe3c:
 vm-scalability.throughput -21.4% regression

Hello,

On Thu 22-02-24 09:32:52, Oliver Sang wrote:
> On Wed, Feb 21, 2024 at 12:14:25PM +0100, Jan Kara wrote:
> > On Tue 20-02-24 16:25:37, kernel test robot wrote:
> > > kernel test robot noticed a -21.4% regression of vm-scalability.throughput on:
> > > 
> > > commit: ab4443fe3ca6298663a55c4a70efc6c3ce913ca6 ("readahead: avoid multiple marked readahead pages")
> > > https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git master
> > > 
> > > testcase: vm-scalability
> > > test machine: 224 threads 2 sockets Intel(R) Xeon(R) Platinum 8480CTDX (Sapphire Rapids) with 512G memory
> > > parameters:
> > > 
> > > 	runtime: 300s
> > > 	test: lru-file-readtwice
> > > 	cpufreq_governor: performance
> > 
> > JFYI I had a look into this. What the test seems to do is that it creates
> > image files on tmpfs, loopmounts XFS there, and does reads over file on
> > XFS. But I was not able to find what lru-file-readtwice exactly does,
> > neither I was able to reproduce it because I got stuck on some missing Ruby
> > dependencies on my test system yesterday.
> 
> what's your OS?

I have SLES15-SP4 installed in my VM. What was missing was 'git' rubygem
which apparently is not packaged at all and when I manually installed it, I
was still hitting other problems so I rather went ahead and checked the
vm-scalability source and wrote my own reproducer based on that.

I'm now able to reproduce the regression in my VM so I'm investigating...

								Honza
-- 
Jan Kara <jack@...e.com>
SUSE Labs, CR