[linus:master] [sched/fair] fb1050ac8e: stress-ng.sleep.ops_per_sec 29.9% regression

[linus:master] [sched/fair] fb1050ac8e: stress-ng.sleep.ops_per_sec 29.9% regression

[kernel test robot]

Hello,

kernel test robot noticed a 29.9% regression of stress-ng.sleep.ops_per_sec on:


commit: fb1050ac8e40aaa014291b5b53612d27890c2b09 ("sched/fair: Change the default cgroup_mode to concur")
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: sleep
  cpufreq_governor: performance


In addition to that, the commit also has significant impact on the following tests:

+------------------+---------------------------------------------------------------------------------------------+
| testcase: change | netperf: netperf.Throughput_Mbps -15.9% regression                                          |
| test machine     | 192 threads 2 sockets Intel(R) Xeon(R) 6740E  CPU @ 2.4GHz (Sierra Forest) with 256G memory |
| test parameters  | cluster=cs-localhost                                                                        |
|                  | cpufreq_governor=performance                                                                |
|                  | ip=ipv4                                                                                     |
|                  | nr_threads=200%                                                                             |
|                  | runtime=300s                                                                                |
|                  | test=TCP_STREAM                                                                             |
+------------------+---------------------------------------------------------------------------------------------+


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@intel.com>
| Closes: https://lore.kernel.org/oe-lkp/202611060925.fb5500b1-lkp@intel.com


Details are as below:
-------------------------------------------------------------------------------------------------->


The kernel config and materials to reproduce are available at:
https://download.01.org/0day-ci/archive/20261106/202611060925.fb5500b1-lkp@intel.com

=========================================================================================
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/sleep/stress-ng/60s

commit: 
  507f910a4e ("sched/fair: Add cgroup_mode: tasks")
  fb1050ac8e ("sched/fair: Change the default cgroup_mode to concur")

507f910a4e1f140a fb1050ac8e40aaa014291b5b536 
---------------- --------------------------- 
         %stddev     %change         %stddev
             \          |                \  
  96108453           -29.9%   67358809        stress-ng.sleep.ops
   1599640           -29.9%    1120640        stress-ng.sleep.ops_per_sec
  46082447           -29.1%   32658369 ±  2%  stress-ng.time.involuntary_context_switches
     15699           -11.3%      13918        stress-ng.time.percent_of_cpu_this_job_got
      6459            -4.7%       6156        stress-ng.time.system_time
      3034           -25.5%       2262        stress-ng.time.user_time
  2.16e+09           -30.6%    1.5e+09        stress-ng.time.voluntary_context_switches


***************************************************************************************************
lkp-srf-2sp3: 192 threads 2 sockets Intel(R) Xeon(R) 6740E  CPU @ 2.4GHz (Sierra Forest) with 256G memory
=========================================================================================
cluster/compiler/cpufreq_governor/ip/kconfig/nr_threads/rootfs/runtime/tbox_group/test/testcase:
  cs-localhost/gcc-14/performance/ipv4/x86_64-rhel-9.4/200%/debian-13-x86_64-20250902.cgz/300s/lkp-srf-2sp3/TCP_STREAM/netperf

commit: 
  507f910a4e ("sched/fair: Add cgroup_mode: tasks")
  fb1050ac8e ("sched/fair: Change the default cgroup_mode to concur")

507f910a4e1f140a fb1050ac8e40aaa014291b5b536 
---------------- --------------------------- 
         %stddev     %change         %stddev
             \          |                \  
      3415           -15.9%       2871        netperf.ThroughputBoth_Mbps
   1311602           -15.9%    1102665        netperf.ThroughputBoth_total_Mbps
      3415           -15.9%       2871        netperf.Throughput_Mbps
   1311602           -15.9%    1102665        netperf.Throughput_total_Mbps
 3.906e+08 ±  2%     -63.2%  1.439e+08 ±  2%  netperf.time.involuntary_context_switches
    184303            -3.2%     178397        netperf.time.minor_page_faults
     11296            +1.6%      11478        netperf.time.percent_of_cpu_this_job_got
     33938            +2.0%      34626        netperf.time.system_time
    444.02 ±  2%     -27.5%     321.87 ±  2%  netperf.time.user_time
    425106 ± 27%     -48.3%     219585 ± 12%  netperf.time.voluntary_context_switches
 3.002e+09           -15.9%  2.524e+09        netperf.workload


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