On Thu, Sep 18, 2025 at 11:29:14AM -0400, Liam R. Howlett wrote:
> * Uladzislau Rezki <[email protected]> [250918 07:50]:
> > On Wed, Sep 17, 2025 at 04:59:41PM -0700, Suren Baghdasaryan wrote:
> > > On Wed, Sep 17, 2025 at 9:14 AM Suren Baghdasaryan <[email protected]>
> > > wrote:
> > > >
> > > > On Tue, Sep 16, 2025 at 10:19 PM Uladzislau Rezki <[email protected]>
> > > > wrote:
> > > > >
> > > > > On Tue, Sep 16, 2025 at 10:09:18AM -0700, Suren Baghdasaryan wrote:
> > > > > > On Mon, Sep 15, 2025 at 8:22 AM Vlastimil Babka <[email protected]>
> > > > > > wrote:
> > > > > > >
> > > > > > > On 9/15/25 14:13, Paul E. McKenney wrote:
> > > > > > > > On Mon, Sep 15, 2025 at 09:51:25AM +0200, Jan Engelhardt wrote:
> > > > > > > >>
> > > > > > > >> On Saturday 2025-09-13 02:09, Sudarsan Mahendran wrote:
> > > > > > > >> >
> > > > > > > >> >Summary of the results:
> > > > > > >
> > > > > > > In any case, thanks a lot for the results!
> > > > > > >
> > > > > > > >> >- Significant change (meaning >10% difference
> > > > > > > >> > between base and experiment) on will-it-scale
> > > > > > > >> > tests in AMD.
> > > > > > > >> >
> > > > > > > >> >Summary of AMD will-it-scale test changes:
> > > > > > > >> >
> > > > > > > >> >Number of runs : 15
> > > > > > > >> >Direction : + is good
> > > > > > > >>
> > > > > > > >> If STDDEV grows more than mean, there is more jitter,
> > > > > > > >> which is not "good".
> > > > > > > >
> > > > > > > > This is true. On the other hand, the mean grew way more in
> > > > > > > > absolute
> > > > > > > > terms than did STDDEV. So might this be a reasonable tradeoff?
> > > > > > >
> > > > > > > Also I'd point out that MIN of TEST is better than MAX of BASE,
> > > > > > > which means
> > > > > > > there's always an improvement for this config. So jitter here
> > > > > > > means it's
> > > > > > > changing between better and more better :) and not between worse
> > > > > > > and (more)
> > > > > > > better.
> > > > > > >
> > > > > > > The annoying part of course is that for other configs it's
> > > > > > > consistently the
> > > > > > > opposite.
> > > > > >
> > > > > > Hi Vlastimil,
> > > > > > I ran my mmap stress test that runs 20000 cycles of mmapping 50
> > > > > > VMAs,
> > > > > > faulting them in then unmapping and timing only mmap and munmap
> > > > > > calls.
> > > > > > This is not a realistic scenario but works well for A/B comparison.
> > > > > >
> > > > > > The numbers are below with sheaves showing a clear improvement:
> > > > > >
> > > > > > Baseline
> > > > > > avg stdev
> > > > > > mmap 2.621073 0.2525161631
> > > > > > munmap 2.292965 0.008831973052
> > > > > > total 4.914038 0.2572620923
> > > > > >
> > > > > > Sheaves
> > > > > > avg stdev avg_diff
> > > > > > stdev_diff
> > > > > > mmap 1.561220667 0.07748897037 -40.44% -69.31%
> > > > > > munmap 2.042071 0.03603083448 -10.94% 307.96%
> > > > > > total 3.603291667 0.113209047 -26.67% -55.99%
> > > > > >
> > > > > Could you run your test with dropping below patch?
> > > >
> > > > Sure, will try later today and report.
> > >
> > > Sheaves with [04/23] patch reverted:
> > >
> > > avg avg_diff
> > > mmap 2.143948 -18.20%
> > > munmap 2.343707 2.21%
> > > total 4.487655 -8.68%
> > >
> > With offloading over sheaves the mmap/munmap is faster, i assume it is
> > because of same objects are reused from the sheaves after reclaim. Whereas
> > we,
> > kvfree_rcu() just free them.
>
> Sorry, I am having trouble following where you think the speed up is
> coming from.
>
> Can you clarify what you mean by offloading and reclaim in this context?
>
[1] <Sheaves series>
avg stdev avg_diff stdev_diff
mmap 1.561220667 0.07748897037 -40.44% -69.31%
munmap 2.042071 0.03603083448 -10.94% 307.96%
total 3.603291667 0.113209047 -26.67% -55.99%
[1] <Sheaves series>
[2] <Sheaves series but with [04/23] patch reverted>
avg avg_diff
mmap 2.143948 -18.20%
munmap 2.343707 2.21%
total 4.487655 -8.68%
[2] <Sheaves series but with [04/23] patch reverted>
I meant those two data results. It is comparison of freeing over
or to "sheaves" and without it in the kvfree_rcu() path.
--
Uladzislau Rezki
