Date: Wed, 26 Mar 2003 01:35:37 -0800 From: Lev Walkin <vlm@netli.com> To: Miguel Mendez <flynn@energyhq.homeip.net> Cc: FreeBSD hackers list <freebsd-hackers@freebsd.org> Subject: Re: Some specific questions about 5.x Message-ID: <3E817469.4030403@netli.com> In-Reply-To: <20030326091845.36425fad.flynn@energyhq.homeip.net> References: <3E815D53.6010404@dynaweb.ru> <20030326091845.36425fad.flynn@energyhq.homeip.net>
next in thread | previous in thread | raw e-mail | index | archive | help
Miguel Mendez wrote: > On Wed, 26 Mar 2003 10:57:07 +0300 > Alex <alex@dynaweb.ru> wrote: > > Howdy. > > >>1. Is it true that kernel threads are more "heavy" than userspace >>ones (pthread) and hence application with hundreds of threads will >>work evidently slower than that using pthreads due to more switching >>penalties? > > > AFAIK, not in a hybrid model. Systems that do 1:1 thread mapping (Like > Gah! Nu/Linux) will suffer from this kind of situation, also will use > more kernel memory. In hybrid implementations based on Scheduler > Activations, like FreeBSD's KSE, and NetBSD's SA, there's a balance > between the number of kernel virtual processors available and the number > of userland threads, it's an N:M model. Nathan Williams' paper on the > subject suggests that context switch is not much slower than a pure > userland implementation. Also, keep in mind that pure userland has other > problems, like when one thread blocks on I/O. In pure userland threading > systems this means the whole process is blocked, whereas in KSE and SA > only that thread is stopped. What about Solaris' migration towards 1:1 model from the N:M one they had supported for years already? Who are insane, Solaris folks (moving towards Linux) or Free/NetBSD ones (migrating to the old Solaris' behavior)? -- Lev Walkin vlm@netli.com
Want to link to this message? Use this URL: <https://mail-archive.FreeBSD.org/cgi/mid.cgi?3E817469.4030403>