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: <462DBEF6.70205@dawes.za.net>
Date:	Tue, 24 Apr 2007 10:25:26 +0200
From:	Rogan Dawes <lists@...es.za.net>
To:	Ingo Molnar <mingo@...e.hu>
Cc:	Linus Torvalds <torvalds@...ux-foundation.org>,
	Nick Piggin <npiggin@...e.de>,
	Gene Heskett <gene.heskett@...il.com>,
	Juliusz Chroboczek <jch@....jussieu.fr>,
	Mike Galbraith <efault@....de>, linux-kernel@...r.kernel.org,
	Peter Williams <pwil3058@...pond.net.au>,
	ck list <ck@....kolivas.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	William Lee Irwin III <wli@...omorphy.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Bill Davidsen <davidsen@....com>, Willy Tarreau <w@....eu>,
	Arjan van de Ven <arjan@...radead.org>
Subject: Re: [REPORT] cfs-v4 vs sd-0.44

Ingo Molnar wrote:
> * Rogan Dawes <lists@...es.za.net> wrote:
> 
>>>        if (p_to && p->wait_runtime > 0) {
>>>                p->wait_runtime >>= 1;
>>>                p_to->wait_runtime += p->wait_runtime;
>>>        }
>>>
>>> the above is the basic expression of: "charge a positive bank balance". 
>>>
>> [..]
>>
>>> [note, due to the nanoseconds unit there's no rounding loss to worry 
>>> about.]
>> Surely if you divide 5 nanoseconds by 2, you'll get a rounding loss?
> 
> yes. But not that we'll only truly have to worry about that when we'll 
> have context-switching performance in that range - currently it's at 
> least 2-3 orders of magnitude above that. Microseconds seemed to me to 
> be too coarse already, that's why i picked nanoseconds and 64-bit 
> arithmetics for CFS.
> 
> 	Ingo

I guess my point was if we somehow get to an odd number of nanoseconds, 
we'd end up with rounding errors. I'm not sure if your algorithm will 
ever allow that.

Rogan
-
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