From: Rene Herman <rene.herman@gmail.com>
To: Jesper Juhl <jesper.juhl@gmail.com>
Cc: Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
Andrew Morton <akpm@osdl.org>, Ingo Molnar <mingo@elte.hu>
Subject: Re: Are we properly prepared to handle 3 Socket setups?
Date: Sun, 12 Aug 2007 05:17:10 +0200 [thread overview]
Message-ID: <46BE7BB6.2010607@gmail.com> (raw)
In-Reply-To: <9a8748490708111852y569a3e18i1c3d192e60eceafe@mail.gmail.com>
On 08/12/2007 03:52 AM, Jesper Juhl wrote:
> On 12/08/07, Rene Herman <rene.herman@gmail.com> 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.
next prev parent reply other threads:[~2007-08-12 3:20 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2007-08-12 1:08 Are we properly prepared to handle 3 Socket setups? Jesper Juhl
2007-08-12 1:27 ` Rene Herman
2007-08-12 1:52 ` Jesper Juhl
2007-08-12 3:17 ` Rene Herman [this message]
2007-08-12 3:29 ` Roland Dreier
2007-08-12 3:36 ` Rene Herman
2007-08-12 8:35 ` Andrew Morton
2007-08-12 20:00 ` Rene Herman
2007-08-13 20:44 ` Christoph Lameter
2007-08-12 7:24 ` Paul Mundt
2007-08-12 8:41 ` Willy Tarreau
2007-08-12 11:46 ` Andi Kleen
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