Re: [RFC][PATCH] Runtime switching of the idle function [take 2]

From: Andi Kleen (ak_at_suse.de)
Date: 11/29/05

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    Date:	Tue, 29 Nov 2005 21:51:09 +0100
To: Lee Revell <rlrevell@joe-job.com>

    On Tue, Nov 29, 2005 at 03:35:39PM -0500, Lee Revell wrote:
    > On Tue, 2005-11-29 at 20:53 +0100, Andi Kleen wrote:
    > > We're mostly addressing it - there are problems left, but
    > > overall it's looking good. The remaining problem is
    > > an education issue of users to not use RDTSC directly,
    > > but use gettimeofday/clock_gettime
    >
    > No the issue is to make gettimeofday fast enough that the people who
    > currently have to use the TSC can use it. Right now it's 1500-3000 nsec
    > or so, Vojtech mentioned that he has a patch that could reduce that to

    It's only that slow if the hardware can't do better.

    And the kernel makes it only slow when using RDTSC directly
    is unsafe - so if you use it directly thinking the kernel cheats
    you for your cycles you're just shoting yourself in the own foot.

    > 150-300 nsec.

    If you have capable hardware it can already do much better.

    -Andi
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