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Message-ID: <20070214121700.GB23857@elf.ucw.cz> Date: Wed, 14 Feb 2007 13:17:00 +0100 From: Pavel Machek <pavel@....cz> To: Bill Davidsen <davidsen@....com> Cc: Jakub Jelinek <jakub@...hat.com>, Arjan van de Ven <arjan@...radead.org>, linux-kernel@...r.kernel.org Subject: Re: [ANN] Userspace M-on-N threading model implementation. Alpha release. Hi! > >>How does that work? Switching between kernel threads requires going into > >>the kernel, user level thread switches are all done in user mode. > >> > >>Do you have some way to change o/s threads w/o going into the kernel? > >> > > > >But going into kernel is not very expensive on Linux. > > > >On the other side, the overhead you need to add for every single syscall > >that might block for the M:N threads and the associated complications > >which make it far harder to conform to POSIX IMHO far outweight the costs > >of going into the kernel for a context switch. > > That really wasn't my question, Arjan said that switching real threads > wasn't a context switch in the hardware sense, and I was asking if I > missed something. It may be cheap, but it would seem to be a context > switch none-the-less. It is not reloading %cr3. Pavel -- (english) http://www.livejournal.com/~pavelmachek (cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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