On Mon, May 15, 2023 at 03:00:44PM +0800, kernel test robot wrote:
> Hello,
>
> kernel test robot noticed a -13.9% regression of will-it-scale.per_thread_ops on:
>
> commit: af7f588d8f7355bc4298dd1962d7826358fc95f0 ("sched: Introduce per-memory-map concurrency ID")
> https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git master
>
> testcase: will-it-scale
> test machine: 224 threads 2 sockets (Sapphire Rapids) with 256G memory
> parameters:
>
> test: context_switch1
> cpufreq_governor: performance
>
> test-description: Will It Scale takes a testcase and runs it from 1 through to n parallel copies to see if the testcase will scale. It builds both a process and threads based test in order to see any differences between the two.
> test-url: https://github.com/antonblanchard/will-it-scale
>
> In addition to that, the commit also has significant impact on the following tests:
>
> +------------------+----------------------------------------------------------------------------------------------------+
> | testcase: change | will-it-scale: will-it-scale.per_thread_ops -73.8% regression |
> | test machine | 224 threads 2 sockets (Sapphire Rapids) with 256G memory |
> | test parameters | cpufreq_governor=performance |
> | | mode=thread |
> | | nr_task=16 |
> | | test=context_switch1 |
> +------------------+----------------------------------------------------------------------------------------------------+
> | testcase: change | will-it-scale: will-it-scale.per_thread_ops -57.9% regression |
> | test machine | 104 threads 2 sockets (Skylake) with 192G memory |
> | test parameters | cpufreq_governor=performance |
> | | mode=thread |
> | | nr_task=16 |
> | | test=context_switch1 |
> +------------------+----------------------------------------------------------------------------------------------------+
> | testcase: change | will-it-scale: will-it-scale.per_thread_ops -85.0% regression |
> | test machine | 104 threads 2 sockets (Skylake) with 192G memory |
> | test parameters | cpufreq_governor=performance |
> | | mode=thread |
> | | nr_task=50% |
> | | test=context_switch1 |
> +------------------+----------------------------------------------------------------------------------------------------+
> | testcase: change | vm-scalability: vm-scalability.throughput -9.0% regression |
> | test machine | 96 threads 2 sockets Intel(R) Xeon(R) Platinum 8260L CPU @ 2.40GHz (Cascade Lake) with 128G memory |
> | test parameters | cpufreq_governor=performance |
> | | runtime=300s |
> | | size=2T |
> | | test=shm-xread-seq-mt |
> +------------------+----------------------------------------------------------------------------------------------------+
>
> FYI, we noticed that commit 223baf9d17f2 (sched: Fix performance
> regression introduced by mm_cid) fixed a sysbench regression, but
> will-it-scale context_switch1 benchmark still saw a regression on this
> fix commit.
>
> Furthermore, we applied the code diff in below link [1] on mainline, and
> the will-it-scale score was restored to the original level before this
> patch.
>
> [1] https://lore.kernel.org/lkml/d96164a6-c522-1bfc-8b37-333726cdc573@xxxxxxxxxxxx/
>
Right; so I'm thinking we can do that patch -- I'll try and get the
whole lazy TLB thing sorted, but I'm not sure I can find the piece and
quiet to think that over in a hurry :/
