linux-kernel - Re: [PATCH v3] srcu: Reduce blocking agressiveness of expedited grace periods further

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Message-ID: <875yjs45g0.wl-maz@kernel.org>
Date:   Wed, 20 Jul 2022 08:19:11 +0100
From:   Marc Zyngier <maz@...nel.org>
To:     paulmck@...nel.org
Cc:     Neeraj Upadhyay <quic_neeraju@...cinc.com>, frederic@...nel.org,
        josh@...htriplett.org, rostedt@...dmis.org,
        mathieu.desnoyers@...icios.com, jiangshanlai@...il.com,
        joel@...lfernandes.org, linux-kernel@...r.kernel.org,
        zhangfei.gao@...mail.com, boqun.feng@...il.com, urezki@...il.com,
        shameerali.kolothum.thodi@...wei.com, pbonzini@...hat.com,
        mtosatti@...hat.com, eric.auger@...hat.com,
        chenxiang66@...ilicon.com, zhangfei.gao@...aro.org,
        rcu@...r.kernel.org
Subject: Re: [PATCH v3] srcu: Reduce blocking agressiveness of expedited grace periods further

Hi Paul,

On Tue, 19 Jul 2022 18:15:47 +0100,
"Paul E. McKenney" <paulmck@...nel.org> wrote:
> 
> On Tue, Jul 19, 2022 at 09:25:56AM +0100, Marc Zyngier wrote:
> >
> > Is there any chance for this fix to make it into 5.19? The regression
> > is significant enough on low-end systems, and I'd rather see it
> > addressed.
> 
> I wasn't planning on it, based on my (possibly quite flawed) assumption
> that it affected only embedded systems running in a virtual environment.

Not quite. This affects any system running virtual machines based on
KVM and using QEMU as the VMM (the machines I run this on don't quite
qualify as "embedded").

> My plan was to send it in my pull request for the next merge window
> next week.  My pull request is next week, yes, the merge window opens
> the following Sunday.  ;-)
> 
> It has a Fixes tag, so it will be backported.
> 
> But if it is important to get it into v5.19 rather than v5.19.x for small
> "x", please let me know and I will see what Linus does with the resulting
> v5.19-rc7 pull request.

I think that the sooner we address this in an upstream kernel, the
better, and I'd definitely support you sending this to Linus for -rc7!

Thanks,

	M.

-- 
Without deviation from the norm, progress is not possible.