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

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Message-ID: <20220720181313.GK1790663@paulmck-ThinkPad-P17-Gen-1>
Date:   Wed, 20 Jul 2022 11:13:13 -0700
From:   "Paul E. McKenney" <paulmck@...nel.org>
To:     Marc Zyngier <maz@...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

On Wed, Jul 20, 2022 at 08:19:11AM +0100, Marc Zyngier wrote:
> 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!

Given your and Zhangfei's Tested-by, if testing continues to go well,
I will send a pull request to Linus before the end of this week.

							Thanx, Paul

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