linux-kernel - Re: [RFC PATCH v1] pin_on_cpu: Introduce thread CPU pinning system call

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Date:   Wed, 22 Jan 2020 12:16:32 -0500 (EST)
From:   Mathieu Desnoyers <mathieu.desnoyers@...icios.com>
To:     Jan Ziak <0xe2.0x9a.0x9b@...il.com>
Cc:     Andi Kleen <andi@...stfloor.org>, Ben Maurer <bmaurer@...com>,
        Boqun Feng <boqun.feng@...il.com>,
        Catalin Marinas <catalin.marinas@....com>,
        Chris Lameter <cl@...ux.com>, Dave Watson <davejwatson@...com>,
        "H. Peter Anvin" <hpa@...or.com>,
        Joel Fernandes <joelaf@...gle.com>,
        Josh Triplett <josh@...htriplett.org>,
        linux-api <linux-api@...r.kernel.org>,
        linux-kernel <linux-kernel@...r.kernel.org>,
        linux-kselftest <linux-kselftest@...r.kernel.org>,
        Russell King <linux@....linux.org.uk>,
        Andy Lutomirski <luto@...capital.net>,
        Ingo Molnar <mingo@...hat.com>,
        Michael Kerrisk <mtk.manpages@...il.com>,
        Paul <paulmck@...ux.vnet.ibm.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Paul Turner <pjt@...gle.com>, rostedt <rostedt@...dmis.org>,
        shuah <shuah@...nel.org>, Thomas Gleixner <tglx@...utronix.de>,
        Will Deacon <will.deacon@....com>
Subject: Re: [RFC PATCH v1] pin_on_cpu: Introduce thread CPU pinning system
 call

(replying again as plain text for mailing lists)

----- On Jan 22, 2020, at 10:44 AM, Jan Ziak 0xe2.0x9a.0x9b@...il.com wrote:

> Hello

> I would like to note that this does not help userspace to express dynamic
> scheduling relationships among processes/threads such as "do not run processes
> A and B on the same core" or "run processes A and B on cores sharing the same
> L2 cache".

Indeed, this is not what this system call is trying to solve. Does the name "pin_on_cpu" lead 
to confusion here ? 

I thought that cgroups was already the mechanism taking care of this kind of requirement. 

Thanks, 

Mathieu 

-- 
Mathieu Desnoyers
EfficiOS Inc.
http://www.efficios.com