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

[Peter Zijlstra]

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@xxxxxxxxx>
> | Closes: https://lore.kernel.org/oe-lkp/202411282207.6bd28eae-lkp@xxxxxxxxx
> 
> 
> 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@xxxxxxxxx
> 
> =========================================================================================
> 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).