Re: [linux-next:master] [mm] 1111d46b5c: stress-ng.pthread.ops_per_sec -84.3% regression

Yang Shi
2023-12-21T18:11:50Z

On Thu, Dec 21, 2023 at 5:40 AM Yin, Fengwei <fengwei.yin@intel.com> wrote:
>
>
>
> On 12/21/2023 8:58 AM, Yin Fengwei wrote:
> > But what I am not sure was whether it's worthy to do such kind of change
> > as the regression only is seen obviously in micro-benchmark. No evidence
> > showed the other regressionsin this report is related with madvise. At
> > least from the perf statstics. Need to check more on stream/ramspeed.
> > Thanks.
>
> With debugging patch (filter out the stack mapping from THP aligned),
> the result of stream can be restored to around 2%:
>
> commit:
> 30749e6fbb3d391a7939ac347e9612afe8c26e94
> 1111d46b5cbad57486e7a3fab75888accac2f072
> 89f60532d82b9ecd39303a74589f76e4758f176f -> 1111d46b5cbad with
> debugging patch
>
> 30749e6fbb3d391a 1111d46b5cbad57486e7a3fab75 89f60532d82b9ecd39303a74589
> ---------------- --------------------------- ---------------------------
> 350993 -15.6% 296081 ± 2% -1.5% 345689
> stream.add_bandwidth_MBps
> 349830 -16.1% 293492 ± 2% -2.3% 341860 ±
> 2% stream.add_bandwidth_MBps_harmonicMean
> 333973 -20.5% 265439 ± 3% -1.7% 328403
> stream.copy_bandwidth_MBps
> 332930 -21.7% 260548 ± 3% -2.5% 324711 ±
> 2% stream.copy_bandwidth_MBps_harmonicMean
> 302788 -16.2% 253817 ± 2% -1.4% 298421
> stream.scale_bandwidth_MBps
> 302157 -17.1% 250577 ± 2% -2.0% 296054
> stream.scale_bandwidth_MBps_harmonicMean
> 339047 -12.1% 298061 -1.4% 334206
> stream.triad_bandwidth_MBps
> 338186 -12.4% 296218 -2.0% 331469
> stream.triad_bandwidth_MBps_harmonicMean
>
>
> The regression of ramspeed is still there.

Thanks for the debugging patch and the test. If no one has objection
to honor MAP_STACK, I'm going to come up with a more formal patch.
Even though thp_get_unmapped_area() is not called for MAP_STACK, stack
area still may be allocated at 2M aligned address theoretically. And
it may be worse with multi-sized THP, for 1M.

Do you have any instructions regarding how to run ramspeed? Anyway I
may not have time debug it until after holidays.

>
>
> Regards
> Yin, Fengwei