linux-kernel - Re: [PATCH v3 0/3] cpu: pseries: Cpu offline states framework

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:	Sat, 26 Sep 2009 07:12:48 +1000
From:	Benjamin Herrenschmidt <benh@...nel.crashing.org>
To:	Peter Zijlstra <a.p.zijlstra@...llo.nl>
Cc:	Gautham R Shenoy <ego@...ibm.com>,
	Joel Schopp <jschopp@...tin.ibm.com>,
	Balbir Singh <balbir@...ibm.com>,
	Venkatesh Pallipadi <venkatesh.pallipadi@...el.com>,
	Dipankar Sarma <dipankar@...ibm.com>,
	Vaidyanathan Srinivasan <svaidy@...ux.vnet.ibm.com>,
	Arun R Bharadwaj <arun@...ux.vnet.ibm.com>,
	linuxppc-dev@...ts.ozlabs.org, linux-kernel@...r.kernel.org,
	"Darrick J. Wong" <djwong@...ibm.com>
Subject: Re: [PATCH v3 0/3] cpu: pseries: Cpu offline states framework

On Fri, 2009-09-25 at 16:48 +0200, Peter Zijlstra wrote:
> On Thu, 2009-09-24 at 10:51 +1000, Benjamin Herrenschmidt wrote:
> > On Tue, 2009-09-15 at 14:11 +0200, Peter Zijlstra wrote:
> > > I still think its a layering violation... its the hypervisor manager
> > > that should be bothered in what state an off-lined cpu is in. 
> > > 
> > That's not how our hypervisor works.
> 
> Then fix it?

Are you serious ? :-)

> CPU hotplug is terribly invasive and expensive to the kernel, doing
> hotplug on a minute basis is just plain crazy.
> 
> If you want a CPU in a keep it near and don't hand it back to the HV
> state, why not use cpusets to isolate it and simply not run tasks on it?
> 
> cpusets don't use stopmachine and are much nicer to the rest of the
> kernel over-all.

Gautham, what is the different in term of power saving between having
it idle for long periods of time (which could do H_CEDE and with NO_HZ,
probably wouln't need to wake up that often) and having it unplugged in
a H_CEDE loop ?

Ben.



--
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/