linux-kernel - Re: [PATCH 1/4] sched: Don't account tickless CPU load on tick

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: <20160201103433.GP6357@twins.programming.kicks-ass.net>
Date:	Mon, 1 Feb 2016 11:34:33 +0100
From:	Peter Zijlstra <peterz@...radead.org>
To:	Byungchul Park <byungchul.park@....com>
Cc:	Frederic Weisbecker <fweisbec@...il.com>,
	LKML <linux-kernel@...r.kernel.org>,
	Chris Metcalf <cmetcalf@...hip.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Luiz Capitulino <lcapitulino@...hat.com>,
	Christoph Lameter <cl@...ux.com>,
	"Paul E . McKenney" <paulmck@...ux.vnet.ibm.com>,
	Mike Galbraith <efault@....de>, Rik van Riel <riel@...hat.com>
Subject: Re: [PATCH 1/4] sched: Don't account tickless CPU load on tick

On Mon, Feb 01, 2016 at 07:05:13PM +0900, Byungchul Park wrote:
> On Fri, Jan 29, 2016 at 10:50:16AM +0100, Peter Zijlstra wrote:
> > On Thu, Jan 28, 2016 at 05:01:26PM +0100, Frederic Weisbecker wrote:
> > > So lets check all the things we call on scheduler_tick():
> > > 
> > > _ sched_clock_tick(): maybe it doesn't need to be called when idle. I'm not sure.
> > >   Some code in idle (timers, irqs, ...) might need to call sched_clock().
> > 
> > Only needed if you've got a shady TSC.
> 
> Yeh.. IMO, this can be done without the tick handling during nohz, with the
> patch I am attaching. Could you check the patch? Or we have to handle it
> remotely, too. (for a crazy TSC)

I think NOHZ_FULL already requires the TSC not to be wrecked.