Re: [linus:master] [fs/pipe] f7f4665dc5: lmbench3.PIPE.bandwidth.MB/sec 18.5% regression

[Christian Brauner <brauner@kernel.org>]

On Thu, Nov 05, 2026 at 08:38:45AM +0800, kernel test robot wrote:
> 
> 
> Hello,
> 
> kernel test robot noticed a 18.5% regression of lmbench3.PIPE.bandwidth.MB/sec on:
> 
> 
> commit: f7f4665dc520fd8bbc1db20e59945773e03744a0 ("fs/pipe: unify the page pools into a single per-pipe pool") https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git master

@Breno can you reproduce this?
It's something we should at least investigate.

> 
> testcase: lmbench3
> config: x86_64-rhel-9.4
> compiler: gcc-14
> test machine: 224 threads 2 sockets Intel(R) Xeon(R) (Sapphire Rapids) with 128G memory
> parameters:
> 
> 	test_memory_size: 50%
> 	nr_threads: 20%
> 	mode: development
> 	test: PIPE
> 	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/202611041404.befe64cd-lkp@intel.com
> 
> Details are as below:
> -------------------------------------------------------------------------------------------------->
> 
> The kernel config and materials to reproduce are available at:
> https://download.01.org/0day-ci/archive/20261104/202611041404.befe64cd-lkp@intel.com
> 
> =========================================================================================
> compiler/cpufreq_governor/kconfig/mode/nr_threads/rootfs/tbox_group/test/test_memory_size/testcase:
>   gcc-14/performance/x86_64-rhel-9.4/development/20%/debian-13-x86_64-20250902.cgz/lkp-spr-2sp2/PIPE/50%/lmbench3
> 
> commit: 
>   c610d2d078 ("fs: annotate inode timestamp accessors")
>   f7f4665dc5 ("fs/pipe: unify the page pools into a single per-pipe pool")
> 
> c610d2d0787961cd f7f4665dc520fd8bbc1db20e599
> ---------------- --------------------------- 
>          %stddev     %change         %stddev
>              \          |                \  
>      29142 ±  2%     -18.5%      23737        lmbench3.PIPE.bandwidth.MB/sec
>     191.80 ±  8%     +54.1%     295.65 ±  5%  lmbench3.time.elapsed_time
>     191.80 ±  8%     +54.1%     295.65 ±  5%  lmbench3.time.elapsed_time.max
>      23261 ± 16%     +19.3%      27743 ±  5%  lmbench3.time.involuntary_context_switches
>       9853 ± 16%     +27.9%      12605 ±  5%  lmbench3.time.system_time
>      51.80 ±  2%     +11.6%      57.80 ±  3%  lmbench3.time.user_time
>  2.928e+08 ±  3%     +26.6%  3.706e+08 ±  4%  lmbench3.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
> 
> 
> 

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