linux-kernel - Re: [PATCH v1 1/6] x86/resctrl: Move __resctrl_sched

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Date: Mon, 8 Apr 2024 20:53:53 -0700
From: Reinette Chatre <reinette.chatre@...el.com>
To: Peter Newman <peternewman@...gle.com>
CC: Fenghua Yu <fenghua.yu@...el.com>, James Morse <james.morse@....com>,
	Stephane Eranian <eranian@...gle.com>, Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>, Dave Hansen
	<dave.hansen@...ux.intel.com>, <x86@...nel.org>, "H. Peter Anvin"
	<hpa@...or.com>, Peter Zijlstra <peterz@...radead.org>, Juri Lelli
	<juri.lelli@...hat.com>, Vincent Guittot <vincent.guittot@...aro.org>,
	Dietmar Eggemann <dietmar.eggemann@....com>, Steven Rostedt
	<rostedt@...dmis.org>, Ben Segall <bsegall@...gle.com>, Mel Gorman
	<mgorman@...e.de>, Daniel Bristot de Oliveira <bristot@...hat.com>, "Valentin
 Schneider" <vschneid@...hat.com>, Uros Bizjak <ubizjak@...il.com>, "Mike
 Rapoport" <rppt@...nel.org>, "Kirill A. Shutemov"
	<kirill.shutemov@...ux.intel.com>, Rick Edgecombe
	<rick.p.edgecombe@...el.com>, Xin Li <xin3.li@...el.com>, Babu Moger
	<babu.moger@....com>, Shaopeng Tan <tan.shaopeng@...itsu.com>, "Maciej
 Wieczor-Retman" <maciej.wieczor-retman@...el.com>, Jens Axboe
	<axboe@...nel.dk>, Christian Brauner <brauner@...nel.org>, Oleg Nesterov
	<oleg@...hat.com>, Andrew Morton <akpm@...ux-foundation.org>, Tycho Andersen
	<tandersen@...flix.com>, Nicholas Piggin <npiggin@...il.com>, Beau Belgrave
	<beaub@...ux.microsoft.com>, "Matthew Wilcox (Oracle)" <willy@...radead.org>,
	<linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v1 1/6] x86/resctrl: Move __resctrl_sched_in() out-of-line

Hi Peter,

On 4/8/2024 2:41 PM, Peter Newman wrote:
> On Mon, Apr 8, 2024 at 1:59 PM Reinette Chatre
> <reinette.chatre@...el.com> wrote:
>> On 4/8/2024 12:05 PM, Peter Newman wrote:
>>> On Sun, Apr 7, 2024 at 12:21 PM Reinette Chatre
>>> <reinette.chatre@...el.com> wrote:

>>> wrappers for the mon and alloc enable keys[1], so I can only assume
>>> they are architecture-independent in concept.
>>
>> The wrappers are intended to be architecture-independent, but the keys
>> are architecture dependent. Quoting the commit you linked to:
>> "This means other architectures don't have to mirror the static keys"
> 
> The static keys seem to exist mainly for the benefit of
> __resctrl_sched_in(), so if it becomes architecture-agnostic, I think
> it would make sense for the static keys to move into the FS code with
> it. I don't see any other usage of these keys in the code that
> remained under arch/x86 on James' latest series.

Good point. James untangled the static keys from multiple usages with
only context switching remaining.
If its only use remains to avoid runtime checks in __resctrl_sched_in()
then it sounds reasonable that the static keys follow
__resctrl_sched_in() to FS code.

Reinette