Re: [linus:master] [sched/core] 118a2cf4ce: stress-ng.schedpolicy.ops_per_sec 14.1% regression

[Paul E. McKenney]

On Fri, Oct 23, 2026 at 07:49:20PM +0800, kernel test robot wrote:
> 
> 
> Hello,
> 
> kernel test robot noticed a 14.1% regression of stress-ng.schedpolicy.ops_per_sec on:
> 
> 
> commit: 118a2cf4ced60777a2408001e2b4838fed1cea55 ("sched/core: Call wakeup_preempt() for queued tasks during class change") https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git master
> 
> testcase: stress-ng
> config: x86_64-rhel-9.4
> compiler: gcc-14
> test machine: 224 threads 2 sockets Intel(R) Xeon(R) Platinum 8480CTDX (Sapphire Rapids) with 256G memory
> parameters:
> 
> 	nr_threads: 100%
> 	testtime: 60s
> 	test: schedpolicy
> 	cpufreq_governor: performance
> 
> 
> 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 <yi1.lai@xxxxxxxxx>
> | Closes: https://lore.kernel.org/oe-lkp/202610231954.51716452-lkp@xxxxxxxxx

This regression is not a good thing, but this commit is fixing a real bug.

								Thanx, Paul

> Details are as below:
> -------------------------------------------------------------------------------------------------->
> 
> 
> The kernel config and materials to reproduce are available at:
> https://download.01.org/0day-ci/archive/20261023/202610231954.51716452-lkp@xxxxxxxxx
> 
> =========================================================================================
> compiler/cpufreq_governor/kconfig/nr_threads/rootfs/tbox_group/test/testcase/testtime:
>   gcc-14/performance/x86_64-rhel-9.4/100%/debian-13-x86_64-20250902.cgz/lkp-spr-r02/schedpolicy/stress-ng/60s
> 
> commit: 
>   v7.3-rc7
>   118a2cf4ce ("sched/core: Call wakeup_preempt() for queued tasks during class change")
> 
>         v7.3-rc7 118a2cf4ced60777a2408001e2b
> ---------------- --------------------------- 
>          %stddev     %change         %stddev
>              \          |                \  
>     246.24           -14.1%     211.56        stress-ng.schedpolicy.SCHED_BATCH_schedules_per_sec
>     246.24           -14.1%     211.56        stress-ng.schedpolicy.SCHED_DEADLINE_schedules_per_sec
>     246.24           -14.1%     211.55        stress-ng.schedpolicy.SCHED_FIFO_schedules_per_sec
>     246.23           -14.1%     211.55        stress-ng.schedpolicy.SCHED_OTHER_schedules_per_sec
>     246.24           -14.1%     211.56        stress-ng.schedpolicy.SCHED_RR_schedules_per_sec
>   16540375           -14.1%   14210394        stress-ng.schedpolicy.ops
>     275785           -14.1%     236940        stress-ng.schedpolicy.ops_per_sec
>      85768 ±  3%    +734.4%     715671 ±  2%  stress-ng.time.involuntary_context_switches
>      32443 ±  2%     +13.9%      36955 ±  2%  stress-ng.time.minor_page_faults
>      21807           -10.3%      19559        stress-ng.time.percent_of_cpu_this_job_got
>      13087           -10.3%      11737        stress-ng.time.system_time
>      78783 ±  2%    +634.5%     578684        stress-ng.time.voluntary_context_switches
> 
> 
> Disclaimer:
> Results have been estimated based on internal Intel analysis and are provided
> for informational purposes only. Any difference in system hardware or software
> design or configuration may affect actual performance.
> 
> 
> -- 
> 0-DAY CI Kernel Test Service
> https://github.com/intel/lkp-tests/wiki
> 
>