linux-kernel - Re: [PATCH 3/4] sched: introduce synchronized idle injection

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: <20151127091702.GA27790@gmail.com>
Date:	Fri, 27 Nov 2015 10:17:02 +0100
From:	Ingo Molnar <mingo@...nel.org>
To:	Jacob Pan <jacob.jun.pan@...ux.intel.com>
Cc:	Peter Zijlstra <peterz@...radead.org>,
	Ingo Molnar <mingo@...hat.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	John Stultz <john.stultz@...aro.org>,
	LKML <linux-kernel@...r.kernel.org>,
	Arjan van de Ven <arjan@...ux.intel.com>,
	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>
Subject: Re: [PATCH 3/4] sched: introduce synchronized idle injection


* Jacob Pan <jacob.jun.pan@...ux.intel.com> wrote:

> On Wed, 18 Nov 2015 09:36:22 +0100
> Ingo Molnar <mingo@...nel.org> wrote:
> 
> > > 
> > > This patch introduces a scheduler based idle injection method, it
> > > works by blocking CFS runqueue synchronously and periodically. The
> > > actions on all online CPUs are orchestrated by per CPU hrtimers.
> > > 
> > > Two sysctl knobs are given to the userspace for selecting the
> > > percentage of idle time as well as the forced idle duration for each
> > > idle period injected.  
> > 
> > What's the purpose of these knobs? Just testing, or will some
> > user-space daemon set them dynamically?
> > 
> yes, it is to be used by userspace daemon such as thermal daemon.
> Though there are interests from in kernel thermal governor but that is
> another story.

Yeah, so let me make this very clear: for a kernel scheduling feature to be 
self-sufficient is not 'another story', but a must-have aspect for this feature
to become upstream acceptable.

We don't add scheduler features that rely on pushing 'policy' to user-space. 
That's poor design with many disadvantages. This feature should offer a reasonable 
and automatic in-kernel default behavior with numbers that prove that it works.

Keeping an essential part of the feature in user-space earns a NAK from me.

Thanks,

	Ingo
--
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/