Re: [PATCH] Dynamic tick for x86 version 050609-2

From: Srivatsa Vaddagiri (vatsa_at_in.ibm.com)
Date: 06/13/05

  • Next message: Hans Korneder: "alarms do not get fired when booting thru pxelinux" 
    Date:	Mon, 13 Jun 2005 22:39:41 +0530
To: Tony Lindgren <tony@atomide.com>

    Hi Tony,
            I went through the dynamic-tick patch on your website
    (patch-dynamic-tick-2.6.12-rc6-050610-1) and was having some
    questions about it:

    1. dyn_tick->skip is set to the number of ticks that have
       to be skipped. This is set on the CPU which is the last
       (in online_map) to go idle and is based on when that
       CPU's next timer is set to expire.

       Other CPUs also seem to use the same interval
       to skip ticks. Shouldnt other CPU check their nearest timer
       rather than blindly skipping dyn_tick->skip number of ticks?

    2. reprogram_apic_timer seems to reprogram the count-down
       APIC timer (APIC_TMICT) with an integral number of apic_timer_val.
       How accurate will this be? Shouldnt this take into account
       that we may not be reprogramming the timer on exactly "jiffy"
       boundary?

    3. Is there any strong reason why you reprogram timers only when
       _all_ CPUs are idle?

    4. In what aspects you think does your patch differ from VST (other
       than not relying on HRT!)? 

    -- 
Thanks and Regards,
Srivatsa Vaddagiri,
Linux Technology Center,
IBM Software Labs,
Bangalore, INDIA - 560017
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