* Avi Kivity <a...@redhat.com> wrote:
> > Also, a profile of a typical kernel build shows:
> >
> > 0.69% cc1 [kernel.kallsyms] [k] clear_page_c
> > 0.49% cc1 [kernel.kallsyms] [k] page_fault
> >
> > So while we could improve it, the question is, can we do this without
> > accidentally slowing things down by more than 0.69%? And kernel
> > builds are a pretty clear_page_c() intense workload.
>
> I usually see much higher clear_page_c, but I'm using a pretty old
> system for most of my testing.
Well, clear_page_c() is still the most expensive kernel function.
I'd suggest using a modern system *and* using percise PEBS profiling
via perf record -e cycles:pp - otherwise it's easy to see profiling
artifacts, especially in and around short functions like
clear_page_c().
Thanks,
Ingo
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