Re: [RFC PATCH V3 0/3] PM/CPU: Parallel enalbing nonboot cpus with resume devices

From: Rafael J. Wysocki
Date: Wed Oct 08 2014 - 17:41:09 EST

On Wednesday, October 08, 2014 10:54:41 PM Peter Zijlstra wrote:
> On Thu, Sep 25, 2014 at 04:32:02PM +0800, Lan Tianyu wrote:
> > This patchset is to parallel enabling nonboot cpus with resuming devices
> > during system resume in order to accelerate S2RAM. From test result on
> > a 8 logical core Haswell machine, system resume time reduces from 347ms
> > to 217ms with this patchset.
> >
> > In the current world, all nonboot cpus are enabled serially during system
> > resume. System resume sequence is that boot cpu enables nonboot cpu one by
> > one and then resume devices. Before resuming devices, there are few tasks
> > assigned to nonboot cpus after they are brought up. This wastes cpu usage.
> >
> > This patchset is to allow boot cpu to go forward to resume devices after
> > bringing up one nonboot cpu and starting a thread. The thread will be in
> > charge of bringing up other frozen cpus. The thread will be scheduled to
> > the first online cpu to run . This makes enabling cpu2~x parallel with
> > resuming devices.
> So I feel we should really clean up hotplug before doing anything like
> this. Its a trainwreck and just piling more and more hacks ontop isn't
> going to help any.


I speak only for myself.
Rafael J. Wysocki, Intel Open Source Technology Center.
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