Date: Tue, 2 Apr 2002 16:47:11 -0500 (EST) From: Kenneth Culver <culverk@alpha.yumyumyum.org> To: Stefan Saroiu <tzoompy@cs.washington.edu> Cc: freebsd-smp@FreeBSD.ORG Subject: Re: Interrupt Handlers and Multiple CPUs Message-ID: <20020402164407.L47960-100000@alpha.yumyumyum.org> In-Reply-To: <20020402132930.B28718-100000@magnesium.cs.washington.edu>
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> Hello, > > This is the context. > > I am writing a packet capture application on a PIV 2GHz single proc > machine with a SK-9843 1Gbps network card. Under 6-700 Mbps of traffic, > 60-70% of the CPU is spent inside of the interrupt handler. This > is the interrupt coming from the NIC (pci/if_sk.c). > > Because so many CPU cycles are spent on these interrupts, the packet > capture application gets starved over time. > > Now the question: > ================ > > If I drop a second CPU in the box, will FreeBSD be smart to schedule the > interrupts on one CPU and the packet capture code on the other? What > FreeBSD version do I need (I have 4.5)? > > The SMP docs on the FreeBSD site seem to point to an affirmative answer, > but I'd like to get more opinions before I blow more money on a second > CPU. > I'm assuming the packet capture code is in userland, and if that's the case, then the answer is "the interrupt handler and the packet cap code may or may not run on the same cpu, meaning they might run on seperate cpu's. This is FreeBSD-4.x. So the answer I guess is maybe but it's not guarunteed to do it all the time, and as far as I know, there's no way to force this behavior. Ken To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-smp" in the body of the message
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