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

[Oliver Sang]

hi, Jan Kara,

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:
> > Hello,
> > 
> > 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?

> 
> Given the workload is over tmpfs, I'm not very concerned about what
> readahead does and how it performs but still I'd like to investigate where
> the regression is coming from because it is unexpected.

Thanks a lot for information!
it was hard to me to determine the connection, so I rebuilt and rerun tests more
which still showed stable data.

if you have any patch want us to try, please let us know.
it's always our great pleasure to supply supports :)

> 
> 								Honza
> -- 
> Jan Kara <jack@xxxxxxxx>
> SUSE Labs, CR
>