From: Andi Kleen <ak@suse.de>
To: Arjan van de Ven <arjan@linux.intel.com>
Cc: mingo@elte.hu, akpm@osdl.org, linux-kernel@vger.kernel.org
Subject: Re: [patch 1/2] round_jiffies infrastructure
Date: 16 Oct 2006 15:42:43 +0200 [thread overview]
Message-ID: <p73wt70cr70.fsf@verdi.suse.de> (raw)
In-Reply-To: <1160496210.3000.310.camel@laptopd505.fenrus.org>
Arjan van de Ven <arjan@linux.intel.com> writes:
> +}
> +EXPORT_SYMBOL_GPL(__round_jiffies);
This means non GPL modules will disturb your timers again. probably not
a good strategy.
> +
> +unsigned long __round_jiffies_relative(unsigned long T, int CPU)
> +{
> + int rem;
> + int original = T;
> + T=T+jiffies;
> + rem = T % HZ;
> + if (rem < HZ/4)
> + T = T - rem;
> + else
> + T = T - rem + HZ;
> + /* we don't want all cpus firing at once hitting the same lock/memory */
> + T += CPU * 3;
Consider a dual core Yonah/Merom: it has shared caches and the two cores
can only go to sleep together. With this the wakeups will be always
twice. Not good. I guess you need to add some topology awareness here
and e.g. only spread it for sockets.
BTW we normally put spaces around operators inside expressions.
-Andi
next prev parent reply other threads:[~2006-10-16 13:42 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
2006-10-10 16:02 [patch 0/2] Introduce round_jiffies() to save spurious wakeups Arjan van de Ven
2006-10-10 16:03 ` [patch 1/2] round_jiffies infrastructure Arjan van de Ven
2006-10-10 16:04 ` [patch 2/2] round_jiffies users Arjan van de Ven
2006-10-10 16:47 ` Ingo Oeser
2006-10-10 16:59 ` Arjan van de Ven
2006-10-10 22:47 ` Paul Dickson
2006-10-10 23:52 ` Arjan van de Ven
2006-10-10 18:56 ` [patch 1/2] round_jiffies infrastructure Andrew Morton
2006-10-10 20:48 ` Arjan van de Ven
2006-10-16 13:42 ` Andi Kleen [this message]
2006-10-11 17:23 ` [patch 0/2] Introduce round_jiffies() to save spurious wakeups Christoph Hellwig
2006-10-11 17:54 ` Arjan van de Ven
2006-10-12 19:02 ` Christoph Hellwig
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