Re: [PCI/MSI] 77e89afc25: will-it-scale.per_process_ops -2.6% regression

[Oliver Sang]

Hi Thomas,

On Fri, Aug 27, 2021 at 12:32:26AM +0200, Thomas Gleixner wrote:
> On Wed, Aug 18 2021 at 22:51, kernel report robot wrote:
> 
> > Greeting,
> >
> > FYI, we noticed a -2.6% regression of will-it-scale.per_process_ops due to commit:
> >
> >
> > commit: 77e89afc25f30abd56e76a809ee2884d7c1b63ce ("PCI/MSI: Protect msi_desc::masked for multi-MSI")
> > https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git master
> >
> >
> > in testcase: will-it-scale
> > on test machine: 128 threads 2 sockets Intel(R) Xeon(R) Gold 6338 CPU @ 2.00GHz with 256G memory
> > with following parameters:
> >
> > 	nr_task: 100%
> > 	mode: process
> > 	test: lseek2
> > 	cpufreq_governor: performance
> > 	ucode: 0xd000280
> >
> > test-description: Will It Scale takes a testcase and runs it from 1 through to n parallel copies to see if the testcase will scale. It builds both a process and threads based test in order to see any differences between the two.
> > test-url: https://github.com/antonblanchard/will-it-scale
> >
> > If you fix the issue, kindly add following tag
> > Reported-by: kernel test robot <oliver.sang@xxxxxxxxx>
> 
> There is nothing to fix. The commit cures an incorrectness. Comparing
> buggy code to correct code is futile.

Got it! the change is a functionality fix. Thanks for information.

> 
> Thanks,
> 
>         tglx