[linus:master] [x86/bugs] a3af84b0fa: stress-ng.seccomp.ops_per_sec 95.7% regression

[linus:master] [x86/bugs] a3af84b0fa: stress-ng.seccomp.ops_per_sec 95.7% regression

[kernel test robot]

Hello,

kernel test robot noticed a 95.7% regression of stress-ng.seccomp.ops_per_sec on:

commit: a3af84b0fa00ead01fcd0e28b5d773ff25990a0d ("x86/bugs: Enable IBPB flush on BPF JIT allocation")
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: 256 threads 2 sockets Intel(R) Xeon(R) 6768P  CPU @ 2.4GHz (Granite Rapids) with 64G memory
parameters:

	nr_threads: 100%
	testtime: 60s
	test: seccomp
	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@intel.com>
| Closes: https://lore.kernel.org/oe-lkp/202608191340.98574fe2-lkp@intel.com


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


The kernel config and materials to reproduce are available at:
https://download.01.org/0day-ci/archive/20260819/202608191340.98574fe2-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-gnr-2sp4/seccomp/stress-ng/60s

commit: 
  96cce16e26 ("bpf: Support for hardening against JIT spraying")
  a3af84b0fa ("x86/bugs: Enable IBPB flush on BPF JIT allocation")
  b72e29e0f7 (bpf: Prefer dirty packs for eBPF allocations)

96cce16e26dd02a8 a3af84b0fa00ead01fcd0e28b5d b72e29e0f7ee329d89f86db8700
---------------- --------------------------- ---------------------------
         %stddev     %change         %stddev     %change         %stddev
             \          |                \          |                \
    351130           -95.7%      15233           -92.8%      25169        stress-ng.seccomp.ops
      5866           -95.7%     252.80           -92.9%     418.07        stress-ng.seccomp.ops_per_sec
    403577           -92.1%      31710           -88.5%      46510        stress-ng.time.involuntary_context_switches
  34288719 ±  2%     -95.4%    1594121           -92.5%    2566499        stress-ng.time.minor_page_faults
      4244           -67.9%       1363 ±  2%     -71.9%       1193        stress-ng.time.percent_of_cpu_this_job_got
      2515           -67.1%     826.95 ±  2%     -71.3%     721.20        stress-ng.time.system_time
     41.17 ±  2%     -94.9%       2.10 ±  3%     -91.7%       3.40 ±  2%  stress-ng.time.user_time
   1119583 ±  2%     -96.3%      40891           -94.5%      61287        stress-ng.time.voluntary_context_switches

Commit b72e29e0f7 slightly recovers performance but remains far below baseline.

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

Re: [linus:master] [x86/bugs] a3af84b0fa: stress-ng.seccomp.ops_per_sec 95.7% regression

[Dave Hansen]

On 8/18/26 23:20, kernel test robot wrote:
> kernel test robot noticed a 95.7% regression of stress-ng.seccomp.ops_per_sec on:

One one level this is a "vulnerability mitigations cause performance
loss, news at 11" kind of thing. Like, Duh!

The microbenchmark here does seem to be a pretty worse-case scenario
where it sits in a loop loading and running a seccomp filter program. In
other words, it's just about as pathological of a test as you can have.

I think Pawan had some more ideas about ways to optimize this. Is there
any appetite for that? Or is the test just too synthetic to worry about?