From: Thomas Gleixner <tglx@linutronix.de>
To: Mats Johannesson <spamcan@bredband.net>
Cc: linux-kernel@vger.kernel.org
Subject: Re: [PATCH] x86-64 highres/dyntick support
Date: Mon, 07 May 2007 17:13:21 +0200 [thread overview]
Message-ID: <1178550801.3042.4.camel@localhost.localdomain> (raw)
In-Reply-To: <20070507140747.2c68d7c9@loke.fish.not>
On Mon, 2007-05-07 at 14:07 +0200, Mats Johannesson wrote:
> This AMD 64 Mobile processor only has a C1 level which isn't used:
>
> root@sleipner:~# cat /proc/acpi/processor/CPU0/power
> active state: C1
> max_cstate: C8
> bus master activity: 00000000
> maximum allowed latency: 2000 usec
> states:
> *C1: type[C1] promotion[--] demotion[--]
> latency[000] usage[00000000] duration[00000000000000000000]
>
> But shouldn't the the kernel 'hlt' routine, or whatever it's called,
> work in conjunction with dyntick to achieve... something...?
To make real power savings from dynticks you need deeper power states in
the CPU. Dyntick can give the idle state code an idea how long the sleep
is going to be, so this code can decide to go into deeper power states
in one go rather than stepping down over time. On a CPU which has no
deeper C states the power saving of dynticks is probably not even
measurable,
tglx
next prev parent reply other threads:[~2007-05-07 15:10 UTC|newest]
Thread overview: 20+ messages / expand[flat|nested] mbox.gz Atom feed top
2007-05-07 12:07 [PATCH] x86-64 highres/dyntick support Mats Johannesson
2007-05-07 15:13 ` Thomas Gleixner [this message]
-- strict thread matches above, loose matches on Subject: below --
2007-05-06 20:58 Thomas Gleixner
2007-05-07 9:16 ` Nicolas Mailhot
2007-05-07 15:28 ` Thomas Gleixner
2007-05-08 17:08 ` Nicolas Mailhot
2007-05-07 16:31 ` Chris Wright
2007-05-07 16:46 ` Thomas Gleixner
2007-05-07 17:18 ` Chris Wright
2007-05-08 9:39 ` Chris Wright
2007-05-08 9:51 ` Thomas Gleixner
2007-05-08 9:51 ` Chris Wright
2007-05-08 9:58 ` Thomas Gleixner
2007-05-08 10:06 ` Chris Wright
2007-05-08 10:34 ` Thomas Gleixner
2007-05-08 13:15 ` Pallipadi, Venkatesh
2007-05-07 22:43 ` Venki Pallipadi
2007-05-07 23:15 ` Thomas Gleixner
2007-05-14 1:17 ` Alistair John Strachan
2007-05-14 6:33 ` Thomas Gleixner
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