Re: [tip:x86/mm] [x86/mm/tlb] 209954cbc7: will-it-scale.per_thread_ops 13.2% regression

Peter Zijlstra
2024-11-28T16:21:34Z

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
>
> [test failed on linux-next/master 6f3d2b5299b0a8bcb8a9405a8d3fceb24f79c4f0]
>
> testcase: will-it-scale
> config: x86_64-rhel-9.4
> compiler: gcc-12
> test machine: 104 threads 2 sockets (Skylake) with 192G memory
> parameters:
>
> nr_task: 100%
> mode: thread
> test: tlb_flush2
> cpufreq_governor: performance
>
>
> In addition to that, the commit also has significant impact on the following tests:
>
> +------------------+------------------------------------------------------------------------------------------------+
> | testcase: change | vm-scalability: vm-scalability.throughput 40.7% regression |
> | test machine | 128 threads 2 sockets Intel(R) Xeon(R) Platinum 8358 CPU @ 2.60GHz (Ice Lake) with 128G memory |
> | test parameters | cpufreq_governor=performance |
> | | nr_ssd=1 |
> | | nr_task=32 |
> | | priority=1 |
> | | runtime=300 |
> | | test=swap-w-seq-mt |
> | | thp_defrag=always |
> | | thp_enabled=never |
> +------------------+------------------------------------------------------------------------------------------------+
>
>
> If you fix the issue in a separate patch/commit (i.e. not just a new version of
> the same patch/commit), kindly add following tags
> | Reported-by: kernel test robot <oliver.sang@intel.com>
> | Closes: https://lore.kernel.org/oe-lkp/202411282207.6bd28eae-lkp@intel.com
>
>
> Details are as below:
> -------------------------------------------------------------------------------------------------->
>
>
> 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).