Date: Thu, 8 Jan 2009 09:16:26 -0500 From: "=?ISO-8859-1?Q?Mehmet_Ali_Aksoy_T=DCYS=DCZ?=" <aksoy.for.research@gmail.com> To: freebsd-hackers@freebsd.org Subject: Re: Threads and SMP kernel scheduling Message-ID: <14ded62c0901080616o68bad18cg256fa10f12c4560b@mail.gmail.com> In-Reply-To: <20090108150807.GA1264@carrot.pvv.ntnu.no> References: <14ded62c0901080123u7268055epb3e17d84aa757051@mail.gmail.com> <20090108150807.GA1264@carrot.pvv.ntnu.no>
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Hi, Thank you very much for your response Ulf. It is a very clear answer. Thank= s again. By the way, any information for the Linux case? Regards, Mehmet On Thu, Jan 8, 2009 at 10:08 AM, Ulf Lilleengen <ulf.lilleengen@gmail.com>w= rote: > On Thu, Jan 08, 2009 at 04:23:08AM -0500, Mehmet Ali Aksoy T=DCYS=DCZ wro= te: > > Hi all, > > > > After I had a bit googling I got confused. > > > > My questions are simple and they are as follows : > > > > 1-) "Are pthreads (or threads in general) of one process scheduled to > > different cores on multi-core systems running Linux or BSD?" > > > The standard threading library in FreeBSD will use a 1:1 mapping between > userland threads(pthreads) and kernel threads. This means that each threa= d > may run on a different core than other threads. > > > 2-) What if there are multiple processes which have multiple threads? > Does > > it change the answer of (1)? > No, the same mapping applies. Although threads of one process may > preferably > run on the same core, each thread of a process may run on any of the core= s > available. > > > > > I found some answers but they are not sharp. Somebody says "can be > > scheduled" but "can be" is not a precise answer (in my opinion.) > Well, it means that there are more factors deciding where a thread is put= . > If > you look at a factor such as affinity, one thread may preferable be > scheduled > to the same core since the cache may contain data relevant to the thread. > > > > > Thanks everybody in advance. > > > Hope everything is at least a bit clearer. > > -- > Ulf Lilleengen >
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