Date: Mon, 25 Feb 2008 20:40:37 -0500 (EST) From: Daniel Eischen <deischen@freebsd.org> To: Jeff Roberson <jroberson@chesapeake.net> Cc: Brooks Davis <brooks@freebsd.org>, Andrew Gallatin <gallatin@cs.duke.edu>, Alfred Perlstein <alfred@freebsd.org>, arch@freebsd.org, Robert Watson <rwatson@freebsd.org>, David Xu <davidxu@freebsd.org> Subject: Re: cpuset and affinity implementation Message-ID: <Pine.GSO.4.64.0802252003060.3971@sea.ntplx.net> In-Reply-To: <20080225143222.B920@desktop> References: <20080220175532.Q920@desktop> <20080220213253.A920@desktop> <20080221092011.J52922@fledge.watson.org> <20080222121253.N920@desktop> <20080222231245.GA28788@lor.one-eyed-alien.net> <20080222134923.M920@desktop> <20080223194047.GB38485@lor.one-eyed-alien.net> <20080223111659.K920@desktop> <20080223213507.GD39699@lor.one-eyed-alien.net> <20080224001902.J920@desktop> <20080225231747.GT99258@elvis.mu.org> <20080225143222.B920@desktop>
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On Mon, 25 Feb 2008, Jeff Roberson wrote: > On Mon, 25 Feb 2008, Alfred Perlstein wrote: > >> Jeff, this is very cool. I do have one issue though: >> >> + * A thread may not be assigned to a a group seperate from other threads >> in >> + * the process. This is to remove ambiguity when the setid is queried >> with >> + * a pid argument. There is no other technical limitation. >> >> Am I understanding things correctly such that within a process there >> can only be one "set"? >> >> If so this restricts some of the benifits you get with sets and >> binding. >> >> An example would be some sort of system with multiple CPUs where some >> are assigned specifically for pseudo-realtime processing and others are for >> general control things such as cli, stats, etc. >> >> In our case we would like to be able to run some threads on specific >> cpu sets, and other threads to be run anywhere on the control CPUs. >> >> Can this be done with this API? > > Individual threads can be bound to any cpu or group of cpus within the set. > So if you just make a set that includes all cpus in the system you can then > bind your realtime threads to specific cpus and the other threads to the > remainder. You will have to specifically bind each thread however. > > The reason individual threads can't be assigned to groups is because > cpuset_getid() for a pid wouldn't make sense then and I expect administrators > to be mostly interested in managing groups of processes. If the administrator sets up a set of CPUs specifically for real-time and another set for non-real-time, you may want to bind some threads to the real-time set, and leave other threads unbound (or even bound to the non-real-time set). In this case, I think cpuset_getid() should either return the default cpuset of all cpus in the system, or the last cpuset to which the process was bound. But regardless, I think binding a thread to a different processor set should be allowed and should override its inherent binding of the process' processor set. Hmm, I guess in this case, a subsequent binding of the process to a processor set should probably override any per-thread bindings. -- DE
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