linux-kernel - Re: [tip:x86/mm] [x86/mm/tlb] 209954cbc7: will-it-scale.per_thread

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Message-ID: <Z0kcZhRuDYQc9Yfu@xsang-OptiPlex-9020>
Date: Fri, 29 Nov 2024 09:44:06 +0800
From: Oliver Sang <oliver.sang@...el.com>
To: Peter Zijlstra <peterz@...radead.org>
CC: Rik van Riel <riel@...riel.com>, <oe-lkp@...ts.linux.dev>,
	<lkp@...el.com>, <linux-kernel@...r.kernel.org>, <x86@...nel.org>, "Ingo
 Molnar" <mingo@...nel.org>, Dave Hansen <dave.hansen@...el.com>, "Linus
 Torvalds" <torvalds@...ux-foundation.org>, Mel Gorman <mgorman@...e.de>,
	<oliver.sang@...el.com>
Subject: Re: [tip:x86/mm] [x86/mm/tlb]  209954cbc7:
 will-it-scale.per_thread_ops 13.2% regression

hi, Peter Zijlstra,

On Thu, Nov 28, 2024 at 05:21:28PM +0100, Peter Zijlstra wrote:
> On Thu, Nov 28, 2024 at 10:57:35PM +0800, kernel test robot wrote:
> > 
> > 
> > Hello,
> > 
> > kernel test robot noticed a 13.2% regression of will-it-scale.per_thread_ops on:
> > 
> > 
> > commit: 209954cbc7d0ce1a190fc725d20ce303d74d2680 ("x86/mm/tlb: Update mm_cpumask lazily")
> > https://git.kernel.org/cgit/linux/kernel/git/tip/tip.git x86/mm
> > 

[...]

> > 
> > 
> > The kernel config and materials to reproduce are available at:
> > https://download.01.org/0day-ci/archive/20241128/202411282207.6bd28eae-lkp@intel.com
> > 
> > =========================================================================================
> > compiler/cpufreq_governor/kconfig/mode/nr_task/rootfs/tbox_group/test/testcase:
> >   gcc-12/performance/x86_64-rhel-9.4/thread/100%/debian-12-x86_64-20240206.cgz/lkp-skl-fpga01/tlb_flush2/will-it-scale
> > 
> > commit: 
> >   7e33001b8b ("x86/mm/tlb: Put cpumask_test_cpu() check in switch_mm_irqs_off() under CONFIG_DEBUG_VM")
> >   209954cbc7 ("x86/mm/tlb: Update mm_cpumask lazily")
> 
> I got a bit lost in the actual jobs descriptions. Are you running this
> test with or without affinity? AFAICT will-it-scale itself defaults to
> being affine (-n is No Affinity).

with affinity. we don't change this default setting.

the command is
python3 ./runtest.py tlb_flush2 295 thread 0 0 104

the first '0' keeps affinity as 'yes'


    print('Usage: runtest.py <testcase> <duration> <mode> <no_affinity> <smt> <threads...>', file=sys.stderr)
    sys.exit(1)
...

affinity = "  "
if int(sys.argv[4]) == 1:
    affinity = " -n "