[linus:master] [nsfs] 82e9343260: stress-ng.signest.ops_per_sec 4.1% regression

[kernel test robot <yi1.lai@intel.com>]

Hello,

kernel test robot noticed a 4.1% regression of stress-ng.signest.ops_per_sec on:


commit: 82e9343260dfc6dda6349f285d9a5eac3e0738d7 ("nsfs: keep namespace tree fields stable until after RCU grace period") 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: signest
	cpufreq_governor: performance


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

+------------------+---------------------------------------------------------------------------------------------+
| testcase: change | stress-ng: stress-ng.sigill.ops_per_sec -3.6% regression                                    |
| test machine     | 224 threads 2 sockets Intel(R) Xeon(R) Platinum 8480CTDX (Sapphire Rapids) with 256G memory |
| test parameters  | cpufreq_governor=performance                                                                |
|                  | nr_threads=100%                                                                             |
|                  | test=sigill                                                                                 |
|                  | testtime=60s                                                                                |
+------------------+---------------------------------------------------------------------------------------------+


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/202610271038.d2f16428-lkp@intel.com


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


The kernel config and materials to reproduce are available at:
https://download.01.org/0day-ci/archive/20261027/202610271038.d2f16428-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/signest/stress-ng/60s

commit: 
  0ecd56573c ("ext4: Avoid entering writeback paths during fastcommit replay")
  82e9343260 ("nsfs: keep namespace tree fields stable until after RCU grace period")

0ecd56573c1f272c 82e9343260dfc6dda6349f285d9
---------------- --------------------------- 
         %stddev     %change         %stddev
             \          |                \  
     33691            +4.3%      35127        stress-ng.signest.nanosec_to_handle_a_signal
 3.989e+08            -4.1%  3.826e+08        stress-ng.signest.ops
   6646641            -4.1%    6374889        stress-ng.signest.ops_per_sec
    147.25            -3.8%     141.70        stress-ng.time.user_time


***************************************************************************************************
lkp-spr-r02: 224 threads 2 sockets Intel(R) Xeon(R) Platinum 8480CTDX (Sapphire Rapids) with 256G memory
=========================================================================================
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/sigill/stress-ng/60s

commit: 
  0ecd56573c ("ext4: Avoid entering writeback paths during fastcommit replay")
  82e9343260 ("nsfs: keep namespace tree fields stable until after RCU grace period")

0ecd56573c1f272c 82e9343260dfc6dda6349f285d9 
---------------- --------------------------- 
         %stddev     %change         %stddev
             \          |                \  
 3.977e+08            -3.6%  3.835e+08        stress-ng.sigill.ops
   6645057            -3.6%    6408021        stress-ng.sigill.ops_per_sec


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