Date: Mon, 9 Oct 2006 00:55:24 +0200 From: "Attilio Rao" <attilio@freebsd.org> To: "John-Mark Gurney" <gurney_j@resnet.uoregon.edu>, "David Xu" <davidxu@freebsd.org>, freebsd-current@freebsd.org, "Kip Macy" <kmacy@fsmware.com>, "Ivan Voras" <ivoras@fer.hr> Subject: Re: [PATCH] MAXCPU alterable in kernel config - needs testers Message-ID: <3bbf2fe10610081555r67265368sf7f12edbf35bff0d@mail.gmail.com> In-Reply-To: <20061008225150.GK793@funkthat.com> References: <2fd864e0610080423q7ba6bdeal656a223e662a5d@mail.gmail.com> <20061008135031.G83537@demos.bsdclusters.com> <4529667D.8070108@fer.hr> <200610090634.31297.davidxu@freebsd.org> <20061008225150.GK793@funkthat.com>
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2006/10/9, John-Mark Gurney <gurney_j@resnet.uoregon.edu>: > David Xu wrote this message on Mon, Oct 09, 2006 at 06:34 +0800: > > On Monday 09 October 2006 04:58, Ivan Voras wrote: > > > Kip Macy wrote: > > > > It will only cover the single chip Niagara 2 boxes. > > > > > > Oh right, they'll doing multi chips in Niagara 2 :) Go Sun :) > > > > > > Still, single T2 chips should be more common, so I'd guess it will pay > > > to optimize for that case. > > > > > > (For the rest of the audience: Niagara 1 has 32 logical CPUs and > > > supports only one physical CPU/socket; Niagara 2 will have 64 logical > > > CPUs and support > 1 CPUs/sockets; so a 2 socket Niagara 2 box will have > > > 128 logical processors! Cue SciFi music...) > > > > > > Any word on how will they handle migration of threads across sockets (or > > > will it be OS's job)? Judging from T1 architecture, I think such event > > > would create a very large performance penalty, but I'm not an expert. > > > __________ > > > > The current 4BSD scheduler does not handle large number of cores very well, > > also the single sched_lock will be a bottleneck for such a configuration. > > Bad enough that Kip had to reduce HZ down to 100... since sched_lock > ends up serializing ALL cpus when scheduling needs to happen.. How would you see a sched_lock decomposition (and, if it is possible, how many locks it could be decomposed in?) Attilio -- Peace can only be achieved by understanding - A. Einstein
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