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

Matthew Wilcox
2023-12-21T04:49:19Z

On Thu, Dec 21, 2023 at 08:58:42AM +0800, Yin Fengwei wrote:
> Yes. MAP_STACK is also mentioned in manpage of mmap. I did test to
> filter out of the MAP_STACK mapping based on this patch. The regression
> in stress-ng.pthread was gone. I suppose this is kind of safe because
> the madvise call is only applied to glibc allocated stack.
>
>
> 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.

FWIW, we had a customer report a significant performance problem when
inadvertently using 2MB pages for stacks. They were able to avoid it by
using 2044KiB sized stacks ...