Re: Severe IRQ problems on Foster (P4 Xeon) system

From: Maciej W. Rozycki (macro@ds2.pg.gda.pl)
Date: Tue Mar 19 2002 - 08:11:55 EST


On Wed, 13 Mar 2002, Ingo Molnar wrote:

> i've written a patch for this, it's enclosed in this email. It implements
> a brownean motion of IRQs, based on load patterns. The concept works
> really well on Foster CPUs - eg. it will redirect IRQs to idle CPUs - but
> if all CPUs are idle then the IRQs are randomly and evenly distributed
> between CPUs.

 A nice idea. One note though -- the code depends on the TSC to be
present. It would be better to use:

if (cpu_has_tsc)
        rdtscll(random_number);

and either preset random_number to a fixed value or even leave it
uninitialized to have it somewhat randomly set by what was found at the
stack for the TSC-less case.

-- 
+  Maciej W. Rozycki, Technical University of Gdansk, Poland   +
+--------------------------------------------------------------+
+        e-mail: macro@ds2.pg.gda.pl, PGP key available        +

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