linux-kernel - Re: [PATCH][resubmit] x86: enable preemption in delay

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] [day] [month] [year] [list]

Message-ID: <20080628104453.GC10872@ucw.cz>
Date:	Sat, 28 Jun 2008 12:44:53 +0200
From:	Pavel Machek <pavel@...e.cz>
To:	Ingo Molnar <mingo@...e.hu>
Cc:	Marin Mitov <mitov@...p.bas.bg>,
	LKML <linux-kernel@...r.kernel.org>,
	Steven Rostedt <rostedt@...dmis.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	linux-rt-users <linux-rt-users@...r.kernel.org>, akpm@...l.org,
	Clark Williams <clark.williams@...il.com>,
	Peter Zijlstra <peterz@...radead.org>,
	"Luis Claudio R. Goncalves" <lclaudio@...g.org>,
	Gregory Haskins <ghaskins@...ell.com>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Andi Kleen <andi-suse@...stfloor.org>
Subject: Re: [PATCH][resubmit] x86: enable preemption in delay

On Wed 2008-06-18 09:55:18, Ingo Molnar wrote:
> 
> * Marin Mitov <mitov@...p.bas.bg> wrote:
> 
> > Why not something like that (do keep in mind I am not an expert :-):
> > 
> > static void delay_tsc(unsigned long loops)
> > {
> > 	get and store the mask of allowed cpus;
> > 	/*     prevent the migration   */
> > 	set the mask of allowed cpus to the current cpu only;
> > 	/*     is it possible? could it be guaranteed?    */
> > 	loop for the delay;
> > 	restore the old mask of allowed cpus;
> > }
> > 
> > You have got the idea. Could it be realized? Is it more expensive than 
> > the current realization? So, comments, please.
> 
> hm, changing/saving/restorig cpus_allowed is really considered a 'heavy' 
> operation compared to preempt_disable(). On a 4096 CPUs box cpus_allowed 
> is 4096 bits which is half a kilobyte ...

Time to RLE the bitmap? 

<runs>							Pavel

-- 
(english) http://www.livejournal.com/~pavelmachek
(cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html
--
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/