linux-kernel - Re: [PATCH 2/4] timer: relax tick stop in idle entry

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]

Date:	Tue, 17 Nov 2015 04:57:21 -0800
From:	Jacob Pan <jacob.jun.pan@...ux.intel.com>
To:	Peter Zijlstra <peterz@...radead.org>
Cc:	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>,
	Arjan van de Ven <arjan@...ux.intel.com>,
	Josh Triplett <josh@...htriplett.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>,
	John Stultz <john.stultz@...aro.org>,
	LKML <linux-kernel@...r.kernel.org>,
	Srinivas Pandruvada <srinivas.pandruvada@...ux.intel.com>,
	Len Brown <len.brown@...el.com>,
	Rafael Wysocki <rafael.j.wysocki@...el.com>,
	Eduardo Valentin <edubezval@...il.com>,
	Paul Turner <pjt@...gle.com>, jacob.jun.pan@...ux.intel.com
Subject: Re: [PATCH 2/4] timer: relax tick stop in idle entry

On Tue, 17 Nov 2015 11:24:49 +0100
Peter Zijlstra <peterz@...radead.org> wrote:

> On Mon, Nov 16, 2015 at 09:04:03PM -0800, Paul E. McKenney wrote:
> > On Mon, Nov 16, 2015 at 06:57:14PM -0800, Arjan van de Ven wrote:
> > > On 11/16/2015 6:53 PM, Paul E. McKenney wrote:
> > > >Fair point.  When in the five-jiffy throttling state, what can
> > > >wake up a CPU?  In an earlier version of this proposal, the
> > > >answer was "nothing", but maybe that has changed.
> > > 
> > > device interrupts are likely to wake the cpus.
> > 
> > OK, that I cannot help you with.  But presumably if the interrupt
> > handler does a wakeup (or similar), that is deferred to the end of
> > the throttling interval?  Timers are also deferred, including
> > hrtimers?
> 
> This throttling thing only throttles 'normal' tasks, real-time tasks
> will still run.

As an optimization or option, it might be useful to further defer the
next timer interrupt if it falls within the idle injection period. But
I guess we don't know if that timer belongs to a normal task or rt.
Also we there could be more than one 'next' timer interrupts fall into
that injection idle period.
--
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/