linux-kernel - Re: [PATCH] Extend mwait idle to optimize away CAL and RES interrupts to an idle CPU -v1

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <1330335058.11248.37.camel@twins>
Date:	Mon, 27 Feb 2012 10:30:58 +0100
From:	Peter Zijlstra <peterz@...radead.org>
To:	Yong Zhang <yong.zhang0@...il.com>
Cc:	Venki Pallipadi <venki@...gle.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>,
	"H. Peter Anvin" <hpa@...or.com>,
	Suresh Siddha <suresh.b.siddha@...el.com>,
	Aaron Durbin <adurbin@...gle.com>,
	Paul Turner <pjt@...gle.com>, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] Extend mwait idle to optimize away CAL and RES
 interrupts to an idle CPU -v1

On Mon, 2012-02-27 at 17:08 +0800, Yong Zhang wrote:
> On Mon, Feb 27, 2012 at 09:38:01AM +0100, Peter Zijlstra wrote:
> > On Fri, 2012-02-24 at 14:13 +0800, Yong Zhang wrote:
> > 
> > > This remind me that we should have moved the irq_enter()/irq_exit() to
> > > each arch's related irq handler.
> > > see: http://marc.info/?l=linux-kernel&m=130709505700821&w=2
> > > 
> > > So Peter, is there someone alread on it? or it still worth doing now?
> > 
> > trouble was that some people didn't feel comfortable adding that
> > overhead to plain resched IPIs that didn't need to do anything.
> 
> Any ideas on where the plain resched IPIs come from?

remote wakeups that don't queue I guess. 

IIRC I looked at it a while back and while not in the majority there
were still a few (I only added counters, didn't look where they came
from).

However since 518cd623 there'd be a lot more I guess..

Feel free to investigate. Also, some non-sched users of the resched ipi
exist, eg. KVM uses it to kick a remote vcpu out from guest mode.
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/