Re: [LKP] [x86, retpolines] ce02ef06fc: will-it-scale.per_thread_ops 3.1% improvement

[Daniel Borkmann]

On 03/13/2019 06:27 AM, kernel test robot wrote:
> Greeting,
> 
> FYI, we noticed a 3.1% improvement of will-it-scale.per_thread_ops due to commit:
> 
> 
> commit: ce02ef06fcf7a399a6276adb83f37373d10cbbe1 ("x86, retpolines: Raise limit for generating indirect calls from switch-case")
> https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git master
> 
> in testcase: will-it-scale
> on test machine: 88 threads Intel(R) Xeon(R) CPU E5-2699 v4 @ 2.20GHz with 64G memory
> with following parameters:
> 
> 	nr_task: 100%
> 	mode: thread
> 	test: futex3
> 	cpufreq_governor: performance
> 	ucode: 0xb00002e
> 
> 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:

Any thoughts on whether the above one-liner gcc work-around should be backported
to stable as well given these gains?

Thanks,
Daniel

> +------------------+---------------------------------------------------------------------------+
> | testcase: change | will-it-scale: will-it-scale.per_process_ops 4.3% improvement             |
> | test machine     | 112 threads Intel(R) Xeon(R) Platinum 8170 CPU @ 2.10GHz with 128G memory |
> | test parameters  | cpufreq_governor=performance                                              |
> |                  | mode=process                                                              |
> |                  | nr_task=50%                                                               |
> |                  | test=futex3                                                               |
> +------------------+---------------------------------------------------------------------------+
> | testcase: change | will-it-scale: will-it-scale.per_process_ops 2.5% improvement             |
> | test machine     | 112 threads Intel(R) Xeon(R) Platinum 8170 CPU @ 2.10GHz with 128G memory |
> | test parameters  | cpufreq_governor=performance                                              |
> |                  | mode=process                                                              |
> |                  | nr_task=50%                                                               |
> |                  | test=futex1                                                               |
> +------------------+---------------------------------------------------------------------------+
> | testcase: change | will-it-scale: will-it-scale.per_process_ops 5.8% improvement             |
> | test machine     | 88 threads Intel(R) Xeon(R) CPU E5-2699 v4 @ 2.20GHz with 64G memory      |
> | test parameters  | cpufreq_governor=performance                                              |
> |                  | mode=process                                                              |
> |                  | nr_task=50%                                                               |
> |                  | test=futex3                                                               |
> +------------------+---------------------------------------------------------------------------+
> | testcase: change | will-it-scale: will-it-scale.per_process_ops 2.6% improvement             |
> | test machine     | 160 threads Intel(R) Xeon(R) CPU E7-8890 v4 @ 2.20GHz with 256G memory    |
> | test parameters  | cpufreq_governor=performance                                              |
> |                  | test=futex1                                                               |
> |                  | ucode=0xb00002e                                                           |
> +------------------+---------------------------------------------------------------------------+
> | testcase: change | will-it-scale: will-it-scale.per_process_ops 2.5% improvement             |
> | test machine     | 112 threads Intel(R) Xeon(R) Platinum 8170 CPU @ 2.10GHz with 128G memory |
> | test parameters  | cpufreq_governor=performance                                              |
> |                  | mode=process                                                              |
> |                  | nr_task=50%                                                               |
> |                  | test=futex2                                                               |
> +------------------+---------------------------------------------------------------------------+
> | testcase: change | will-it-scale: will-it-scale.per_thread_ops 3.1% improvement              |
> | test machine     | 88 threads Intel(R) Xeon(R) CPU E5-2699 v4 @ 2.20GHz with 64G memory      |
> | test parameters  | cpufreq_governor=performance                                              |
> |                  | mode=thread                                                               |
> |                  | nr_task=50%                                                               |
> |                  | test=futex4                                                               |
> +------------------+---------------------------------------------------------------------------+
> | testcase: change | will-it-scale: will-it-scale.per_thread_ops 5.4% improvement              |
> | test machine     | 88 threads Intel(R) Xeon(R) CPU E5-2699 v4 @ 2.20GHz with 64G memory      |
> | test parameters  | cpufreq_governor=performance                                              |
> |                  | mode=thread                                                               |
> |                  | nr_task=16                                                                |
> |                  | test=futex3                                                               |
> +------------------+---------------------------------------------------------------------------+
> | testcase: change | will-it-scale: will-it-scale.per_thread_ops 3.0% improvement              |
> | test machine     | 88 threads Intel(R) Xeon(R) CPU E5-2699 v4 @ 2.20GHz with 64G memory      |
> | test parameters  | cpufreq_governor=performance                                              |
> |                  | mode=thread                                                               |
> |                  | nr_task=16                                                                |
> |                  | test=futex4                                                               |
> +------------------+---------------------------------------------------------------------------+