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: <p73bqaf2bpb.fsf@bingen.suse.de>
Date:	Wed, 31 Oct 2007 22:53:04 +0100
From:	Andi Kleen <andi@...stfloor.org>
To:	Peter Zijlstra <a.p.zijlstra@...llo.nl>
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

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.

-Andi
-
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/