On 08/12/2007 03:52 AM, Jesper Juhl wrote:
On 12/08/07, Rene Herman <[email protected]> wrote:
On 08/12/2007 03:08 AM, Jesper Juhl wrote:
This may be a little off topic, but I think it's interresting enough
to warrent a single mail.
I just saw a news article (http://www.theinquirer.net/?article=41610)
about a 3 Socket Opteron motherboard and couldn't help but wonder if
we are prepared to deal with such a beast, so I thought I'd inform
everyone :-)
I'm guessing equipping such a board with 3 single core CPU's could
show up some interresting corner cases in schedular code and
elsewhere, I'll bet we have some assumptions somewhere about
nr_of_cpus being an even number...
I would hope the N=1 case will have flushed out enough of those... :-|
Hehe, true, but I was thinking more of nr_of_cpus is an odd number > 1. :-)
Just thinking of having to divide things by 3 makes me worry ;-) ...
It's not a hugely strange worry no. Grepping around (for num_online_cpus for
example) didn't throw up any glaring bugs I believe.
A possible problem in mm/vmstat.c:calculate_threshold() where 3 CPUs would
be treated as 2 through an fls(). No idea about that code and if that would
be a problem.
The line just below where it does that _does_ seem to have a problem:
/*
* Maximum threshold is 125
*/
threshold = min(125, threshold);
as either the comment or the code is wrong and it seems it's the code. Added
Andrew Morton to the CC for that.
CFS (v19.1) has an ilog2 on num_online_cpus() in
kernel/sched.c:sched_init_granularity() but this seems not a problem. Added
Ingo Molnar.
Rene.
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