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From: Peter Newman <peternewman@google.com>
Date: Thu, 11 Apr 2024 15:44:10 -0700
Message-ID: <CALPaoCj1QVtVYcVV2FS1muL9Lo7f1MXuXaQQ+WKRi8h42aCCjw@mail.gmail.com>
Subject: Re: [PATCH v1 0/6] x86/resctrl: Avoid searching tasklist during mongrp_reparent
To: babu.moger@amd.com
Cc: Fenghua Yu <fenghua.yu@intel.com>, Reinette Chatre <reinette.chatre@intel.com>, 
	James Morse <james.morse@arm.com>, Stephane Eranian <eranian@google.com>, 
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Hi Babu,

On Thu, Apr 11, 2024 at 3:34=E2=80=AFPM Moger, Babu <bmoger@amd.com> wrote:
>
> Hi Peter,
>
> On 3/25/2024 12:27 PM, Peter Newman wrote:
> > To avoid this issue, this series replaces the CLOSID and RMID values
> > cached in the task_struct with a pointer to the task's rdtgroup, throug=
h
> > which the current CLOSID and RMID can be obtained indirectly during a
> > context switch. Updating a group's ID then only requires the current
> > task to be switched back in on all CPUs. On server hosts with very larg=
e
> > thread counts, this is much less disruptive than making thread creation
> > globally unavailable. However, this is less desirable on CPU-isolated,
> > realtime workloads, so I am interested in suggestions on how to reach a
> > compromise for the two use cases.
>
> Before going this route, have you thought about your original solution
> where CONTROL_MON groups sharing the same CLOSID?
>
> [3] https://lore.kernel.org/lkml/CALPaoCj-zav4x6H3ffXo_O+RFan8Qb-uLy-Ddtk=
aQTfuxY4a0w@mail.gmail.com
>
> May be it is less disruptive than changing the context switch code.. Thou=
ghts?

If had I ever posted that series, it would have contained the very
same changes to the context switch code, because that solution causes
rdtgroup->closid fields to change on almost every schemata write.

-Peter