Re: [PATCH RFC v2 00/10] SLUB percpu sheaves
From: Suren Baghdasaryan
Date: Fri Mar 14 2025 - 13:10:42 EST
On Tue, Mar 4, 2025 at 11:08 AM Liam R. Howlett <Liam.Howlett@xxxxxxxxxx> wrote:
>
> * Vlastimil Babka <vbabka@xxxxxxx> [250304 05:55]:
> > On 2/25/25 21:26, Suren Baghdasaryan wrote:
> > > On Mon, Feb 24, 2025 at 1:12 PM Suren Baghdasaryan <surenb@xxxxxxxxxx> wrote:
> > >>
> > >> >
> > >> > > The values represent the total time it took to perform mmap syscalls, less is
> > >> > > better.
> > >> > >
> > >> > > (1) baseline control
> > >> > > Little core 7.58327 6.614939 (-12.77%)
> > >> > > Medium core 2.125315 1.428702 (-32.78%)
> > >> > > Big core 0.514673 0.422948 (-17.82%)
> > >> > >
> > >> > > (2) baseline control
> > >> > > Little core 7.58327 5.141478 (-32.20%)
> > >> > > Medium core 2.125315 0.427692 (-79.88%)
> > >> > > Big core 0.514673 0.046642 (-90.94%)
> > >> > >
> > >> > > (3) baseline control
> > >> > > Little core 7.58327 4.779624 (-36.97%)
> > >> > > Medium core 2.125315 0.450368 (-78.81%)
> > >> > > Big core 0.514673 0.037776 (-92.66%)
> > >
> > > (4) baseline control
> > > Little core 7.58327 4.642977 (-38.77%)
> > > Medium core 2.125315 0.373692 (-82.42%)
> > > Big core 0.514673 0.043613 (-91.53%)
> > >
> > > I think the difference between (3) and (4) is noise.
> > > Thanks,
> > > Suren.
> >
> > Hi, as we discussed yesterday, it would be useful to set the baseline to
> > include everything before sheaves as that's already on the way to 6.15, so
> > we can see more clearly what sheaves do relative to that. So at this point
> > it's the vma lock conversion including TYPESAFE_BY_RCU (that's not undone,
> > thus like in scenario (4)), and benchmark the following:
> >
> > - baseline - vma locking conversion with TYPESAFE_BY_RCU
> > - baseline+maple tree node reduction from mm-unstable (Liam might point out
> > which patches?)
>
> Sid's patches [1] are already in mm-unstable.
>
>
> > - the above + this series + sheaves enabled for vm_area_struct cache
> > - the above + full maple node sheaves conversion [1]
> > - the above + the top-most patches from [1] that are optimizations with a
> > tradeoff (not clear win-win) so it would be good to know if they are useful
> >
> > [1] currently the 4 commits here:
> > https://web.git.kernel.org/pub/scm/linux/kernel/git/vbabka/linux.git/log/?h=slub-percpu-sheaves-v2-maple
> > from "maple_tree: Sheaf conversion" to "maple_tree: Clean up sheaf"
> > but as Liam noted, they won't cherry pick without conflict once maple tree
> > node reduction is backported, but he's working on a rebase
>
> Rebased maple tree sheaves, patches are here [2].
Hi Folks,
Sorry for the delay. I got the numbers last week but they looked a bit
weird, so I reran the test increasing the number of iterations to make
sure noise is not a factor. That took most of this week. Below are the
results. Please note that I had to backport the patchsets to 6.12
because that's the closest stable Android kernel I can use. I measure
cumulative time to execute mmap syscalls, so the smaller the number
the better mmap performance is:
baseline: 6.12 + vm_lock conversion and TYPESAFE_BY_RCU
config1: baseline + Sid's patches [1]
config2: sheaves RFC
config3: config1 + vm_area_struct with sheaves
config4: config2 + maple_tree Sheaf conversion [2]
config5: config3 + 2 last optimization patches from [3]
config1 config2 config3 config4 config5
Little core -0.10% -10.10% -12.89% -10.02% -13.64%
Mid core -21.05% -37.31% -44.97% -15.81% -22.15%
Big core -17.17% -34.41% -45.68% -11.39% -15.29%
[1] https://lore.kernel.org/linux-mm/20250227204823.758784-1-sidhartha.kumar@xxxxxxxxxx/
[2] https://www.infradead.org/git/?p=users/jedix/linux-maple.git;a=shortlog;h=refs/heads/sheaves_rebase_20250304
[3] https://web.git.kernel.org/pub/scm/linux/kernel/git/vbabka/linux.git/log/?h=slub-percpu-sheaves-v2-maple
>From the numbers, it looks like config4 regresses the performance and
that's what looked weird to me last week and I wanted to confirm this.
But from sheaves POV, it looks like they provide the benefits I saw
before. Sid's patches which I did not test separately before also look
beneficial.
Thanks,
Suren.
>
>
> >
> >
> ...
>
> Thanks,
> Liam
>
> [1]. https://lore.kernel.org/linux-mm/20250227204823.758784-1-sidhartha.kumar@xxxxxxxxxx/
> [2]. https://www.infradead.org/git/?p=users/jedix/linux-maple.git;a=shortlog;h=refs/heads/sheaves_rebase_20250304