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Re: dynamic-hz

From:  Andrew Morton <akpm-AT-osdl.org>
To:  Con Kolivas <kernel-AT-kolivas.org>
Subject:  Re: dynamic-hz
Date:  Mon, 13 Dec 2004 03:02:37 -0800
Cc:  andrea-AT-suse.de, pavel-AT-suse.cz, linux-kernel-AT-vger.kernel.org
Archive-link:  Article, Thread

Con Kolivas <kernel@kolivas.org> wrote:
>
> The performance benefit, if any, is often lost in noise during 
>  benchmarks and when there, is less than 1%. So I was wondering if you 
>  had some specific advantage in mind for this patch? Is there some 
>  arch-specific advantage? I can certainly envision disadvantages to lower
Hz.

There are apparently some laptops which exhibit appreciable latency between
the start of ACPI sleep and actually consuming less power.  The 1ms wakeup
frequency will shorten battery life on these machines significantly.  (I
forget the exact numbers - Len will know).

So I guess we're going to have to do this sometime - I don't think there's
any other solution apart from going fully tickless, which would be
considerably more intrusive.

We should retain the option of compile-time constant HZ - it's
easy enough.  Probably the patch already does that.


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