linux-kernel - Re: [PATCH 3/6] sched: high-res preemption tick

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: <1193868271.5911.5.camel@lappy>
Date:	Wed, 31 Oct 2007 23:04:31 +0100
From:	Peter Zijlstra <a.p.zijlstra@...llo.nl>
To:	Andi Kleen <andi@...stfloor.org>
Cc:	linux-kernel@...r.kernel.org, Ingo Molnar <mingo@...e.hu>,
	Mike Galbraith <efault@....de>,
	Dmitry Adamushko <dmitry.adamushko@...il.com>,
	Thomas Gleixner <tglx@...utronix.de>
Subject: Re: [PATCH 3/6] sched: high-res preemption tick


On Wed, 2007-10-31 at 22:53 +0100, Andi Kleen wrote:
> Peter Zijlstra <a.p.zijlstra@...llo.nl> writes:
> 
> > Use HR-timers (when available) to deliver an accurate preemption tick.
> >
> > The regular scheduler tick that runs at 1/HZ can be too coarse when nice
> > level are used. The fairness system will still keep the cpu utilisation 'fair'
> > by then delaying the task that got an excessive amount of CPU time but try to
> > minimize this by delivering preemption points spot-on.
> 
> This might be costly when hrtimers happen to use an more expensive
> to reprogram time source. Even an APIC timer access is fairly slow. 
> And you'll potentially add the to lots of context switces.
> 
> Not sure that is a good idea for performance in general.

Well, me neither, it was just an idea, and a challenge to get
working :-)



-
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/