linux-kernel - Re: [patch] x86: scale cyc_2_nsec according to CPU frequency

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: <20071207152741.3408aeef@inria.fr>
Date:	Fri, 7 Dec 2007 15:27:41 +0100
From:	Guillaume Chazarain <guichaz@...oo.fr>
To:	Ingo Molnar <mingo@...e.hu>
Cc:	Thomas Gleixner <tglx@...utronix.de>,
	Stefano Brivio <stefano.brivio@...imi.it>,
	Robert Love <rml@...h9.net>, linux-kernel@...r.kernel.org,
	Dave Jones <davej@...hat.com>,
	"Rafael J. Wysocki" <rjw@...k.pl>, Michael Buesch <mb@...sch.de>,
	Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: [patch] x86: scale cyc_2_nsec according to CPU frequency

Le Fri, 7 Dec 2007 14:55:25 +0100,
Ingo Molnar <mingo@...e.hu> a écrit :

> Firstly, we dont need the 'offset' anymore because cpu_clock() maintains 
> offsets itself.

Yes, but a lower quality one. __update_rq_clock tries to compensate
large jumping clocks with a jiffy resolution, while my offset arranges
for a very smooth frequency transition.

I agree with keeping a single offset, but I liked the fact that with my
patch on frequency change, the clock had no jump at all.

> + *  ns += offset to avoid sched_clock jumps with cpufreq

I guess this needs to go away if I don't make my point :-(

> +	printk("CPU#%d: changed cyc2ns scale from %ld to %ld\n",
> +		cpu, prev_scale, *scale);

Pointing it out just to be sure it does not end in the final version ;-)

Thanks for cleaning up my mess ;-)

-- 
Guillaume
--
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/