On Wed, 26 Mar 2003 10:57:07 +0300 Alex <[EMAIL PROTECTED]> 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. > 2. Is it true that even 5.x has no implementation for inter-process > semaphores that are blocking calling thread only not the whole process > as usually in FreeBSD? That I don't know, perhaps the local KSE guru, Julian might have an answer for this. Cheers, -- Miguel Mendez - [EMAIL PROTECTED] GPG Public Key :: http://energyhq.homeip.net/files/pubkey.txt EnergyHQ :: http://www.energyhq.tk Tired of Spam? -> http://www.trustic.com
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