linux-kernel - Re: [PATCH RFC v2 00/10] SLUB percpu sheaves

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Message-ID: <ape445nrqgod4ivtzcwacmfdshi3fgcqmmu54iascbjsk3sluo@w4jjihiz5jzr>
Date: Tue, 4 Mar 2025 14:08:38 -0500
From: "Liam R. Howlett" <Liam.Howlett@...cle.com>
To: Vlastimil Babka <vbabka@...e.cz>
Cc: Suren Baghdasaryan <surenb@...gle.com>,
        Kent Overstreet <kent.overstreet@...ux.dev>,
        Christoph Lameter <cl@...ux.com>, David Rientjes <rientjes@...gle.com>,
        Roman Gushchin <roman.gushchin@...ux.dev>,
        Hyeonggon Yoo <42.hyeyoo@...il.com>,
        Uladzislau Rezki <urezki@...il.com>, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org, rcu@...r.kernel.org,
        maple-tree@...ts.infradead.org,
        Sebastian Andrzej Siewior <bigeasy@...utronix.de>,
        Alexei Starovoitov <ast@...nel.org>
Subject: Re: [PATCH RFC v2 00/10] SLUB percpu sheaves

* Vlastimil Babka <vbabka@...e.cz> [250304 05:55]:
> On 2/25/25 21:26, Suren Baghdasaryan wrote:
> > On Mon, Feb 24, 2025 at 1:12 PM Suren Baghdasaryan <surenb@...gle.com> 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].

> 
> 
...

Thanks,
Liam

[1]. https://lore.kernel.org/linux-mm/20250227204823.758784-1-sidhartha.kumar@oracle.com/
[2]. https://www.infradead.org/git/?p=users/jedix/linux-maple.git;a=shortlog;h=refs/heads/sheaves_rebase_20250304