Re: [linus:master] [btrfs] b7fdfd29a1: postmark.transactions 9.5% regression

[Qu Wenruo <quwenruo.btrfs@gmx.com>]

在 2025/10/27 18:11, kernel test robot 写道:
> 
> 
> Hello,
> 
> kernel test robot noticed a 9.5% regression of postmark.transactions on:
> 
> 
> commit: b7fdfd29a136a17c5c8ad9e9bbf89c48919c3d19 ("btrfs: only set the device specific options after devices are opened")
> https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git master
> 
> 
> we are in fact not sure what's the connection between this change and the
> postmark.transactions performance. still report out due to below checks.
> 
> [still regression on      linus/master 4bb1f7e19c4a1d6eeb52b80acff5ac63edd1b91d]
> [regression chould be solved by reverting this commit on linus/master head]
> [still regression on linux-next/master 72fb0170ef1f45addf726319c52a0562b6913707]
> 
> testcase: postmark
> config: x86_64-rhel-9.4
> compiler: gcc-14
> test machine: 224 threads 4 sockets Intel(R) Xeon(R) Platinum 8380H CPU @ 2.90GHz (Cooper Lake) with 192G memory
> parameters:
> 
> 	disk: 1HDD
> 	fs: btrfs
> 	fs1: nfsv4
> 	number: 4000n
> 	trans: 10000s
> 	subdirs: 100d
> 	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 <oliver.sang@intel.com>
> | Closes: https://lore.kernel.org/oe-lkp/202510271449.efa21738-lkp@intel.com
> 
> 
> Details are as below:
> -------------------------------------------------------------------------------------------------->
> 
> 
> The kernel config and materials to reproduce are available at:
> https://download.01.org/0day-ci/archive/20251027/202510271449.efa21738-lkp@intel.com
> 
> =========================================================================================
> compiler/cpufreq_governor/disk/fs1/fs/kconfig/number/rootfs/subdirs/tbox_group/testcase/trans:
>    gcc-14/performance/1HDD/nfsv4/btrfs/x86_64-rhel-9.4/4000n/debian-13-x86_64-20250902.cgz/100d/lkp-cpl-4sp2/postmark/10000s
> 
> commit:
>    53a4acbfc1 ("btrfs: fix memory leak on duplicated memory in the qgroup assign ioctl")

This is definitely not related.

>    b7fdfd29a1 ("btrfs: only set the device specific options after devices are opened")

But this may affect performance, because without this fix, btrfs always 
falls back to `ssd` mount option

Now it will properly detect rotating devices, and won't set `ssd` mount 
option by default.

But if this is causing performance drop, we should really consider if 
`ssd` should be the only mode we support.

Thanks,
Qu

> 
> 53a4acbfc1de85fa b7fdfd29a136a17c5c8ad9e9bbf
> ---------------- ---------------------------
>           %stddev     %change         %stddev
>               \          |                \
>        2010           +10.5%       2222        nfsstat.Client.nfs.v4.open_noat
>       97983 ± 11%     +18.5%     116101        numa-numastat.node1.other_node
>       97983 ± 11%     +18.5%     116101        numa-vmstat.node1.numa_other
>       16001 ±  5%      -7.5%      14797 ±  5%  sched_debug.cfs_rq:/.load.avg
>     1474354 ±  3%      +9.9%    1620281 ±  4%  sched_debug.cpu.avg_idle.avg
>      756151 ±  3%     +10.0%     831539 ±  4%  sched_debug.cpu.max_idle_balance_cost.avg
>        3585            -2.6%       3490        perf-stat.i.context-switches
>        6141 ±  2%      +4.0%       6385        perf-stat.i.cycles-between-cache-misses
>        5796 ±  2%      +3.9%       6024        perf-stat.overall.cycles-between-cache-misses
>        3580            -2.6%       3486        perf-stat.ps.context-switches
>   9.548e+11            +7.3%  1.025e+12        perf-stat.total.instructions
>      136494            +4.3%     142419        proc-vmstat.nr_inactive_file
>      136494            +4.3%     142419        proc-vmstat.nr_zone_inactive_file
>     2784208            +4.8%    2917180        proc-vmstat.numa_hit
>     2435763            +5.5%    2568673        proc-vmstat.numa_local
>     3042276            +5.1%    3196281        proc-vmstat.pgalloc_normal
>     2627503            +6.9%    2808220        proc-vmstat.pgfault
>     2754381            +5.4%    2903034        proc-vmstat.pgfree
>       97857            +6.3%     104058        proc-vmstat.pgreuse
>        9.80            -9.4%       8.88        postmark.creation_mixed_trans
>      112312            -7.0%     104473        postmark.data_read
>      203502            -7.0%     189298        postmark.data_written
>        9.80            -9.4%       8.88        postmark.deletion_mixed_trans
>        9.73            -9.5%       8.80        postmark.files_appended
>       12.59            -7.0%      11.70        postmark.files_created
>       12.59            -7.0%      11.70        postmark.files_deleted
>        9.87            -9.5%       8.93        postmark.files_read
>      715.35            +7.5%     768.93        postmark.time.elapsed_time
>      715.35            +7.5%     768.93        postmark.time.elapsed_time.max
>       51508            -1.6%      50690        postmark.time.voluntary_context_switches
>       19.61            -9.5%      17.75        postmark.transactions
> 
> 
> 
> 
> 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.
> 
>