linux-kernel - Re: [PATCH v3 09/21] slab: add optimized sheaf refill from partial list

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Message-ID: <1390b9ce-0ed1-4cc9-845f-fa4dd5f3ffc8@suse.cz>
Date: Tue, 20 Jan 2026 11:32:57 +0100
From: Vlastimil Babka <vbabka@...e.cz>
To: Harry Yoo <harry.yoo@...cle.com>
Cc: Petr Tesarik <ptesarik@...e.com>, Christoph Lameter <cl@...two.org>,
 David Rientjes <rientjes@...gle.com>,
 Roman Gushchin <roman.gushchin@...ux.dev>, Hao Li <hao.li@...ux.dev>,
 Andrew Morton <akpm@...ux-foundation.org>,
 Uladzislau Rezki <urezki@...il.com>,
 "Liam R. Howlett" <Liam.Howlett@...cle.com>,
 Suren Baghdasaryan <surenb@...gle.com>,
 Sebastian Andrzej Siewior <bigeasy@...utronix.de>,
 Alexei Starovoitov <ast@...nel.org>, linux-mm@...ck.org,
 linux-kernel@...r.kernel.org, linux-rt-devel@...ts.linux.dev,
 bpf@...r.kernel.org, kasan-dev@...glegroups.com
Subject: Re: [PATCH v3 09/21] slab: add optimized sheaf refill from partial
 list

On 1/20/26 11:27, Harry Yoo wrote:
> On Tue, Jan 20, 2026 at 07:33:47AM +0100, Vlastimil Babka wrote:
>> 
>> Right, so the plan was to set min to some fraction of max when refilling
>> sheaves, with the goal of maximizing the chance that once we grab a slab
>> from the partial list, we almost certainly fully use it and don't have to
>> return it back.
> 
> Oh, you had a plan!
> 
> I'm having trouble imagining what it would look like though.
> If we fetch more objects than `to_fill`, where do they go?
> Have a larger array and fill multiple sheaves with it?

Ah that wouldn't happen. Rather we would consider sheaf to be full even if
it was filled a bit below its capacity, if trying to reach the full capacity
would mean taking a slab from partial list, not using all objects from it
and having to return it to the list.
Of course this would not apply for a prefilled sheaf request or
kmem_cache_alloc_bulk().

>> But I didn't get to there yet. It seems worthwile to try
>> though so we can leave the implementation prepared for it?
> 
> Yeah that's fine.
>