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: <alpine.DEB.2.11.1505201518050.4225@nanos>
Date:	Wed, 20 May 2015 15:20:13 +0200 (CEST)
From:	Thomas Gleixner <tglx@...utronix.de>
To:	Ingo Molnar <mingo@...nel.org>
cc:	Borislav Petkov <bp@...e.de>, Huang Rui <ray.huang@....com>,
	Len Brown <lenb@...nel.org>,
	"Rafael J. Wysocki" <rjw@...ysocki.net>, x86@...nel.org,
	linux-kernel@...r.kernel.org,
	Fengguang Wu <fengguang.wu@...el.com>,
	Aaron Lu <aaron.lu@...el.com>, Tony Li <tony.li@....com>,
	Frédéric Weisbecker <fweisbec@...il.com>
Subject: Re: [RFC PATCH 2/4] x86, mwaitt: introduce mwaitx idle with a
 configurable timer

On Wed, 20 May 2015, Ingo Molnar wrote:
> * Borislav Petkov <bp@...e.de> wrote:
> 
> > On Wed, May 20, 2015 at 01:11:20PM +0200, Ingo Molnar wrote:
> > >   - MWAITX takes a 'timeout' parameter, but otherwise behaves exactly 
> > >     like MWAIT: i.e. once idle it won't exit idle on its own
> > 
> > Let me quote the commit message:
> > 
> > "MWAITT, another name is MWAITX (MWAIT with extensions), has a
> > configurable timer that causes MWAITX to exit on expiration."
> 
> Ah. A useful skill that is, being able to read.
> 
> > You need to set the second bit in ECX to enable the timer.
> > 
> > I guess if you don't, then you get normal MWAIT but then you don't 
> > need the timeout either...
> 
> Yeah.
> 
> So if it's a true timeout then we could use it to implement irq-less 
> timers: that's actually pretty useful, because it could be faster than 
> getting a local APIC timer irq, etc.

Uurgh, NO NO NO! 

We have enough trouble with non functional timers already, we do not
need another variant of those.

We can supply the estimated sleep time though if that helps the PM
controller underneath to select a state. That's more or less what we
do in the governors as well.

Thanks,

	tglx
--
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/

Powered by blists - more mailing lists

Powered by Openwall GNU/*/Linux Powered by OpenVZ