From mboxrd@z Thu Jan 1 00:00:00 1970 From: Christoph Hellwig Date: Sat, 04 Sep 2004 16:55:16 +0000 Subject: Re: [PATCH 2/4] SGI Altix cross partition functionality (1st revision) Message-Id: <20040904175516.A16490@infradead.org> List-Id: References: <20040616163514.GB27891@sgi.com> In-Reply-To: <20040616163514.GB27891@sgi.com> MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: linux-ia64@vger.kernel.org On Sat, Sep 04, 2004 at 11:35:11AM -0500, Russ Anderson wrote: > Perhaps I'm missing what you mean by "complexity". I understand that a reasonable > way to modify a mono-CPU kernel to run on a dual-CPU system is to add a big > kernel lock. And that as the number of CPUs increase, the locks need to be > finer grain to avoid excessive lock contention. And that identifying and > breaking up the hot locks is a part of that process. Cray went through > that process with COS, unicos, SGI with Irix, and now the community > with Linux. > > What Dean is doing, and what the Cray and SGI people have learned over > the last couple decades of hard work, is that it is simpler and less complex > to design in fine grain locks to avoid scaling problems. We know that CPUs > will get faster, the number of CPUs will increase, as will the number of nodes > and amount of memory. And as they increase, we know that big locks will get > hot and need to broken up. So that is why you will find people that > believe that it is simpler and less complex to design in fine grain locks, > to avoid having to track down and fix scaling bugs. Have you not looked at the code or are you publically trying to make a fool of yourself? The lock is taken during xfc_connect/disconnect which happen exactly at ifconfig up/down time. Please explain me why ifconfig scalability matters to SGI.