linux-kernel - Re: [PATCH RFC] sched: Add a per-thread core scheduling interface(Internet mail)

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Date:   Thu, 21 May 2020 04:09:50 +0000
From:   benbjiang(蒋彪) 
        <benbjiang@...cent.com>
To:     "Joel Fernandes (Google)" <joel@...lfernandes.org>
CC:     Nishanth Aravamudan <naravamudan@...italocean.com>,
        Julien Desfossez <jdesfossez@...italocean.com>,
        Peter Zijlstra <peterz@...radead.org>,
        "Tim Chen" <tim.c.chen@...ux.intel.com>,
        "mingo@...nel.org" <mingo@...nel.org>,
        "tglx@...utronix.de" <tglx@...utronix.de>,
        "pjt@...gle.com" <pjt@...gle.com>,
        "torvalds@...ux-foundation.org" <torvalds@...ux-foundation.org>,
        vpillai <vpillai@...italocean.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "fweisbec@...il.com" <fweisbec@...il.com>,
        "keescook@...omium.org" <keescook@...omium.org>,
        "kerrnel@...gle.com" <kerrnel@...gle.com>,
        Phil Auld <pauld@...hat.com>, Aaron Lu <aaron.lwe@...il.com>,
        Aubrey Li <aubrey.intel@...il.com>,
        "aubrey.li@...ux.intel.com" <aubrey.li@...ux.intel.com>,
        Valentin Schneider <valentin.schneider@....com>,
        Mel Gorman <mgorman@...hsingularity.net>,
        Pawan Gupta <pawan.kumar.gupta@...ux.intel.com>,
        Paolo Bonzini <pbonzini@...hat.com>,
        Joel Fernandes <joelaf@...gle.com>
Subject: Re: [PATCH RFC] sched: Add a per-thread core scheduling
 interface(Internet mail)



> On May 21, 2020, at 6:26 AM, Joel Fernandes (Google) <joel@...lfernandes.org> wrote:
> 
> Add a per-thread core scheduling interface which allows a thread to tag
> itself and enable core scheduling. Based on discussion at OSPM with
> maintainers, we propose a prctl(2) interface accepting values of 0 or 1.
> 1 - enable core scheduling for the task.
> 0 - disable core scheduling for the task.
> 
> Special cases:
> (1)
> The core-scheduling patchset contains a CGroup interface as well. In
> order for us to respect users of that interface, we avoid overriding the
> tag if a task was CGroup-tagged because the task becomes inconsistent
> with the CGroup tag. Instead return -EBUSY.
> 
> (2)
> If a task is prctl-tagged, allow the CGroup interface to override
> the task's tag.
> 
> ChromeOS will use core-scheduling to securely enable hyperthreading.
> This cuts down the keypress latency in Google docs from 150ms to 50ms
> while improving the camera streaming frame rate by ~3%.
Hi,
Are the performance improvements compared to the hyperthreading disabled scenario or not?
Could you help to explain how the keypress latency improvement comes with core-scheduling?

Thanks a lot.

Regards,
Jiang