linux-kernel - Re: [PATCH v8 1/2] sched: Add per_cpu cluster domain info and cpus_share_lowest

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Date:   Tue, 30 May 2023 21:24:58 +0800
From:   Yicong Yang <yangyicong@...wei.com>
To:     Peter Zijlstra <peterz@...radead.org>
CC:     <yangyicong@...ilicon.com>, <mingo@...hat.com>,
        <juri.lelli@...hat.com>, <vincent.guittot@...aro.org>,
        <dietmar.eggemann@....com>, <tim.c.chen@...ux.intel.com>,
        <yu.c.chen@...el.com>, <gautham.shenoy@....com>, <mgorman@...e.de>,
        <vschneid@...hat.com>, <linux-kernel@...r.kernel.org>,
        <linux-arm-kernel@...ts.infradead.org>, <rostedt@...dmis.org>,
        <bsegall@...gle.com>, <bristot@...hat.com>,
        <prime.zeng@...wei.com>, <jonathan.cameron@...wei.com>,
        <ego@...ux.vnet.ibm.com>, <srikar@...ux.vnet.ibm.com>,
        <linuxarm@...wei.com>, <21cnbao@...il.com>,
        <kprateek.nayak@....com>, <wuyun.abel@...edance.com>,
        Barry Song <song.bao.hua@...ilicon.com>
Subject: Re: [PATCH v8 1/2] sched: Add per_cpu cluster domain info and
 cpus_share_lowest_cache API

On 2023/5/30 19:38, Peter Zijlstra wrote:
> On Tue, May 30, 2023 at 03:02:52PM +0800, Yicong Yang wrote:
>> From: Barry Song <song.bao.hua@...ilicon.com>
>>
>> Add per-cpu cluster domain info and cpus_share_lowest_cache() API.
> 
> Lowest cache is weird; that would be L1, but your implementation is for
> L2/L3.
> 

ok there seems a history about this naming.

In the first version we make it cpus_share_cluster(), since on non-cluster
machine it actually behaves as cpus_share_cache() so "cluster" maybe inaccurate.
Then we make it cpus_share_resources() [1]. Tim mentioned cpus_share_lowest_cache()
maybe more informative in [2] so we use it.

Since lowest cache may refer to L1 as mentioned, maybe we should use
cpus_share_resources() again to avoid confusion?

[1] https://lore.kernel.org/lkml/CAKfTPtBKLDyNPXg7uLbQ3jUnEwppfC+E29=oJ1tWzzqHsNpApw@mail.gmail.com/
[2] https://lore.kernel.org/lkml/05472b4ed10c694bce1a2b6dd4a0ef13ea337db3.camel@linux.intel.com/

Thanks,
Yicong