Re: io apic + tsc = slowdown (bugreport + possible fix)

From: john stultz (johnstul_at_us.ibm.com)
Date: 06/29/04

  • Next message: David Mosberger: "Re: [profile]: [10/23] ia64 profiling cleanups" 
    To: "Maciej W. Rozycki" <macro@linux-mips.org>
Date:	Tue, 29 Jun 2004 11:52:58 -0700

    On Tue, 2004-06-29 at 05:07, Maciej W. Rozycki wrote:
    > On Mon, 28 Jun 2004, john stultz wrote:
    >
    > > Looking closer at the proposed workaround by Maciej posted here:
    > > http://linux.derkeiler.com/Mailing-Lists/Kernel/2004-04/3174.html
    > >
    > > Why exactly are we using cpu_has_tsc to switch this? I'm not sure I'm
    > > following how this is TSC dependent. Additionally the comment change
    > > looks to be from the 2.4 era.
    >
    > One of the two users of timer_ack is do_slow_gettimeoffset(). When the
    > TSC is selected for use as a high-precision timer do_fast_gettimeoffset()
    > is used instead.
    >
    > Please folks do read the sources sometimes -- I've been repeatedly
    > clarifying these bits while they are all documented in the sources,
    > sigh...

    Whoops, sorry, I had the impression the patch was targeted against 2.6,
    where there is no do_slow_gettimeoffset() and the only user of timer_ack
    is in do_timer_interrupt().

    So am I incorrect that the TSC bits can be dropped for the 2.6 version
    of the patch?

    thanks
    -john

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