linux-kernel - Re: [PATCH] driver core: Use unbound workqueue for deferred probes

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Message-ID: <a40db2a2-f58a-aaec-6976-977d4b9f9e0e@codeaurora.org>
Date:   Thu, 25 Feb 2021 16:03:50 +0530
From:   Yogesh Lal <ylal@...eaurora.org>
To:     Greg KH <gregkh@...uxfoundation.org>
Cc:     rafael@...nel.org, linux-kernel@...r.kernel.org,
        linux-arm-msm@...r.kernel.org, pkondeti@...eaurora.org,
        neeraju@...eaurora.org
Subject: Re: [PATCH] driver core: Use unbound workqueue for deferred probes

Hi Greg,

On 2/24/2021 6:13 PM, Greg KH wrote:
> On Wed, Feb 24, 2021 at 05:25:49PM +0530, Yogesh Lal wrote:
>> Queue deferred driver probes on unbounded workqueue, to allow
>> scheduler better manage scheduling of long running probes.
> 
> Really?  What does this change and help?  What is the visable affect of
> this patch?  What problem does it solve?
> 

We observed boot up improvement (~400 msec) when the deferred probe work 
is made unbound. This is due to scheduler moving the worker running 
deferred probe work to big CPUs. without this change, we see the worker 
is running on LITTLE CPU due to affinity.

Please let us now if there are any concerns/restrictions that deferred 
probe work should run only on pinned kworkers. Since this work runs 
deferred probe of several devices , the locality may not be that important

Thanks
Yogesh Lal

> thanks,
> 
> greg k-h
> 

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