From owner-freebsd-hackers Tue Aug 7 9:55:15 2001 Delivered-To: freebsd-hackers@freebsd.org Received: from earth.backplane.com (earth-nat-cw.backplane.com [208.161.114.67]) by hub.freebsd.org (Postfix) with ESMTP id 067C637B40C; Tue, 7 Aug 2001 09:55:11 -0700 (PDT) (envelope-from dillon@earth.backplane.com) Received: (from dillon@localhost) by earth.backplane.com (8.11.4/8.11.2) id f77Gt9M32808; Tue, 7 Aug 2001 09:55:09 -0700 (PDT) (envelope-from dillon) Date: Tue, 7 Aug 2001 09:55:09 -0700 (PDT) From: Matt Dillon Message-Id: <200108071655.f77Gt9M32808@earth.backplane.com> To: Terry Lambert Cc: Mike Smith , Zhihui Zhang , freebsd-hackers@freebsd.org Subject: Re: Allocate a page at interrupt time References: <200108070739.f777dmi08218@mass.dis.org> <3B6FB0AE.8D40EF5D@mindspring.com> Sender: owner-freebsd-hackers@FreeBSD.ORG Precedence: bulk List-ID: List-Archive: (Web Archive) List-Help: (List Instructions) List-Subscribe: List-Unsubscribe: X-Loop: FreeBSD.ORG :> > It also has the unfortunate property of locking us into virtual :> > wire mode, when in fact Microsoft demonstrated that wiring down :> > interrupts to particular CPUs was good practice, in terms of :> > assuring best performance. Specifically, running in virtual :> > wire mode means that all your CPUs get hit with the interrupt, :> > whereas running with the interrupt bound to a particular CPU :> > reduces the overall overhead. Even what we have today, with :> > the big giant lock and redirecting interrupts to "the CPU in :> > the kernel" is better than that... :> :> Terry, this is *total* garbage. :> :> Just so you know, ok? : :What "this", exactly? : :That "virtual wire" mode is actually a bad idea for some :applications -- specifically, high speed networking with :multiple gigabit ethernet cards? All the cpu's don't get the interrupt, only one does. :That Microsoft demonstrated that wiring down interrupts :to a particular CPU was a good idea, and kicked both Linux' :and FreeBSD's butt in the test at ZD Labs? Well, if you happen to have four NICs and four CPUs, and you are running them all full bore, I would say that wiring the NICs to the CPUs would be a good idea. That seems like a rather specialized situation, though. -Matt :That taking interrupts on a single directed CPU is better :than taking an IPI on all your CPUs, and then sorting out :who's going to handle the interrupt? :... : :-- Terry To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-hackers" in the body of the message