Re: [PATCH 0/3] slab: support memoryless nodes with sheaves

[Jon Hunter]

Hi Vlastimil,

On 11/03/2026 17:22, Vlastimil Babka (SUSE) wrote:
> On 3/11/26 10:49, Ming Lei wrote:
> > On Wed, Mar 11, 2026 at 09:25:54AM +0100, Vlastimil Babka (SUSE) wrote:
> > > This is the draft patch from [1] turned into a proper series with
> > > incremental changes. It's based on v7.0-rc3. It's too intrusive for a
> > > 7.0 hotfix, so we'll only be able to fix/reduce the regression in 7.1. I
> > > hope it's acceptable given it's a non-standard configuration, 7.0 is not
> > > a LTS, and it's a perf regression, not functionality.
> > >
> > > Ming can you please retest this on top of v7.0-rc3, which already has
> > > fb1091febd66 ("mm/slab: allow sheaf refill if blocking is not
> > > allowed"). Separate data point for v7.0-rc3 could be also useful.
> > >
> > > [1] https://lore.kernel.org/all/c6a01f7e-c6eb-454b-9b9e-734526dd659d@xxxxxxxxxx/
> > >
> > > Signed-off-by: Vlastimil Babka (SUSE) <vbabka@xxxxxxxxxx>
> > > ---
> > > Vlastimil Babka (SUSE) (3):
> > >        slab: decouple pointer to barn from kmem_cache_node
> > >        slab: create barns for online memoryless nodes
> > >        slab: free remote objects to sheaves on memoryless nodes
> >
> > Hi Vlastimil and Guys,
> >
> > I re-run the test case used in https://lore.kernel.org/all/aZ0SbIqaIkwoW2mB@fedora/
> >
> > - v6.19-rc5: 34M
> >
> > - 815c8e35511d Merge branch 'slab/for-7.0/sheaves' into slab/for-next: 13M
> >
> > - v7.0-rc3: 13M
>
> Thanks, that's in line with your previous testing of "mm/slab: allow sheaf
> refill if blocking is not allowed" making no difference here. At least we
> just learned it helps other benchmarks :)
>
> > - v7.0-rc3 + the three patches: 24M
>
> OK. So now it might be really the total per-cpu caching capacity difference.


I have also observed a performance regresssion for Linux v7.0-rc for 
some graphics related tests we run. I bisected to ...

# first bad commit: [e47c897a29491ade20b27612fdd3107c39a07357] slab: add 
sheaves to most caches

I came across Ming's report and hence, found this series. I have also 
tested the 3 patches in this series and it did appear to help with one 
test, but overall I am still seeing a ~25% performance regression (the 
tests are taking about 25% longer to run). I am not the owner or author 
of these specific tests and I have not dived into see exactly what is 
taking longer, but I just know they are taking longer to run.

Anyway, I have not seen any recent updates on this, and so I am not sure 
if there are any other updates or what the current status of this is?

If there are any more patches available I will be happy to test.

Thanks!
Jon

--
nvpublic