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SubjectRe: [PATCH] thp: reduce usage of huge zero page's atomic counter
On Tue, 30 Aug 2016 11:09:15 +0800 Aaron Lu <aaron.lu@intel.com> wrote:

> >> Case used for test on Haswell EP:
> >> usemem -n 72 --readonly -j 0x200000 100G
> >> Which spawns 72 processes and each will mmap 100G anonymous space and
> >> then do read only access to that space sequentially with a step of 2MB.
> >>
> >> perf report for base commit:
> >> 54.03% usemem [kernel.kallsyms] [k] get_huge_zero_page
> >> perf report for this commit:
> >> 0.11% usemem [kernel.kallsyms] [k] mm_get_huge_zero_page
> >
> > Does this mean that overall usemem runtime halved?
>
> Sorry for the confusion, the above line is extracted from perf report.
> It shows the percent of CPU cycles executed in a specific function.
>
> The above two perf lines are used to show get_huge_zero_page doesn't
> consume that much CPU cycles after applying the patch.
>
> >
> > Do we have any numbers for something which is more real-wordly?
>
> Unfortunately, no real world numbers.
>
> We think the global atomic counter could be an issue for performance
> so I'm trying to solve the problem.

So, umm, we don't actually know if the patch is useful to anyone?

Some more measurements would help things along, please.

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