lkml.org 
[lkml]   [2002]   [Mar]   [15]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
From
SubjectRe: [PATCH] 2.4.18 scheduler bugs
Date
>>> but even in the Athlon case an IPI is still an IRQ entry, which will add
>>> at least 200 cycles or more to the idle wakeup latency.
>>
>> It is an idle cpu that is spending those 200 cycles.
>
> wrong. When it's woken up it's *not* an idle CPU anymore, and it's the
> freshly woken up task that is going to execute 200 cycles later...

I have to disagree. It is the woken up task *running on the
otherwise idle CPU* that burns up 200 cycles at the tail.

A cpu is wasting, say, 5,000,000 cycles (1GHz/100/2, or 1/2 tick) in
hlt when it could have been doing work. Why worry about an
alternative wakeup path that burns up 200-400 cycles of that on the
otherwise idling cpu, even if it is at the tail.

Joe
-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/

\
 
 \ /
  Last update: 2005-03-22 13:24    [W:1.028 / U:0.012 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site