linux-kernel - Re: [PATCH 07/10] sched: Migrate sched to use new tick dependency mask model

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: <20150804074116.GH25159@twins.programming.kicks-ass.net>
Date:	Tue, 4 Aug 2015 09:41:16 +0200
From:	Peter Zijlstra <peterz@...radead.org>
To:	Frederic Weisbecker <fweisbec@...il.com>
Cc:	LKML <linux-kernel@...r.kernel.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	Preeti U Murthy <preeti@...ux.vnet.ibm.com>,
	Christoph Lameter <cl@...ux.com>,
	Ingo Molnar <mingo@...nel.org>,
	Viresh Kumar <viresh.kumar@...aro.org>,
	Rik van Riel <riel@...hat.com>
Subject: Re: [PATCH 07/10] sched: Migrate sched to use new tick dependency
 mask model

On Mon, Aug 03, 2015 at 07:30:32PM +0200, Frederic Weisbecker wrote:
> > But you've forgotten about SCHED_DEADLINE, we count those in:
> > rq->dl.dl_nr_running.
> 
> Indeed. Hmm, there is no preemption between SCHED_DEALINE tasks, right?
> So I can treat it like SCHED_FIFO.

Sadly no. Even though EDF has static job priority (once a job is
activated its priority doesn't change anymore) DEADLINE also has a CBS
component and that needs the tick regardless, even with a single task.

So any deadline task running means we cannot stop the tick.
--
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/