linux-kernel - RE: [PATCH 3/4] mm/slub: simplify get_partial

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Date: Wed, 3 Apr 2024 11:15:44 +0000
From: "Song, Xiongwei" <Xiongwei.Song@...driver.com>
To: Vlastimil Babka <vbabka@...e.cz>,
        "rientjes@...gle.com"
	<rientjes@...gle.com>,
        "cl@...ux.com" <cl@...ux.com>,
        "penberg@...nel.org"
	<penberg@...nel.org>,
        "iamjoonsoo.kim@....com" <iamjoonsoo.kim@....com>,
        "akpm@...ux-foundation.org" <akpm@...ux-foundation.org>,
        "roman.gushchin@...ux.dev" <roman.gushchin@...ux.dev>,
        "42.hyeyoo@...il.com"
	<42.hyeyoo@...il.com>
CC: "linux-mm@...ck.org" <linux-mm@...ck.org>,
        "linux-kernel@...r.kernel.org"
	<linux-kernel@...r.kernel.org>,
        "chengming.zhou@...ux.dev"
	<chengming.zhou@...ux.dev>
Subject: RE: [PATCH 3/4] mm/slub: simplify get_partial_node()

> 
> On 4/3/24 2:37 AM, Song, Xiongwei wrote:
> >>
> >>
> >> It could be tempting to use >= instead of > to achieve the same effect but
> >> that would have unintended performance effects that would best be evaluated
> >> separately.
> >
> > I can run a test to measure Amean changes. But in terms of x86 assembly, there
> > should not be extra  instructions with ">=".
> >
> > Did a simple test, for ">=" it uses "jle" instruction, while "jl" instruction is used for ">".
> > No more instructions involved. So there should not be performance effects on x86.
> 
> Right, I didn't mean the code of the test, but how the difference of the
> comparison affects how many cpu partial slabs would be put on the cpu
> partial list here.

Got it. Will do measurement for it.

Thanks,
Xiongwei