linux-kernel - Re: [PATCH v1] PM: sleep: Restore asynchronous device resume optimization

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Message-ID: <ZcPSuUBoL_EDvcTF@slm.duckdns.org>
Date: Wed, 7 Feb 2024 08:58:01 -1000
From: Tejun Heo <tj@...nel.org>
To: Marek Szyprowski <m.szyprowski@...sung.com>
Cc: "Rafael J. Wysocki" <rafael@...nel.org>,
	"Rafael J. Wysocki" <rjw@...ysocki.net>,
	Linux PM <linux-pm@...r.kernel.org>,
	Ulf Hansson <ulf.hansson@...aro.org>,
	Nathan Chancellor <nathan@...nel.org>,
	LKML <linux-kernel@...r.kernel.org>,
	Stanislaw Gruszka <stanislaw.gruszka@...ux.intel.com>,
	Lai Jiangshan <jiangshanlai@...il.com>, Naohiro.Aota@....com,
	kernel-team@...a.com
Subject: Re: [PATCH v1] PM: sleep: Restore asynchronous device resume
 optimization

On Wed, Feb 07, 2024 at 07:55:51PM +0100, Marek Szyprowski wrote:
> On 07.02.2024 17:39, Tejun Heo wrote:
> > On Wed, Feb 07, 2024 at 12:25:46PM +0100, Rafael J. Wysocki wrote:
> >> The other one is that what happens during async resume does not meet
> >> the assumptions of commit 5797b1c18919 (for example, it can easily
> >> produce a chain of interdependent work items longer than 8) and so it
> >> breaks things.
> > Ah, that's fascinating. But aren't CPUs all brought up online before devices
> > are resumed? If so, the max_active should already be way higher than the
> > WQ_DFL_MIN_ACTIVE. Also, are these multi node NUMA machines? Otherwise, it
> > really shouldn't affect anything. One easy way to verify would be just
> > bumping up WQ_DFL_MIN_ACTIVE and see what happens.
> 
> I've increased WQ_DFL_MIN_ACTIVE from 8 to 32 and all the system 
> suspend/resume issues went away. :)

Ah, okay, that's surprising. Lemme look at the code again. I gotta be
missing something.

Thanks.

-- 
tejun