Date: Fri, 19 Mar 1999 22:06:35 -0800 From: Amancio Hasty <hasty@rah.star-gate.com> To: Matthew Dillon <dillon@apollo.backplane.com> Cc: Julian Elischer <julian@whistle.com>, Bill Paul <wpaul@skynet.ctr.columbia.edu>, hackers@FreeBSD.ORG Subject: Re: Gigabit ethernet revisited Message-ID: <199903200606.WAA38098@rah.star-gate.com> In-Reply-To: Your message of "Fri, 19 Mar 1999 20:13:07 PST." <199903200413.UAA16399@apollo.backplane.com>
next in thread | previous in thread | raw e-mail | index | archive | help
I think that David Greeman quoted 2 gigabytes/sec memory bandwith for the Xeon processor with whatever chipset he was using. Cheers, Amancio > :Bill Paul wrote: > :> > :> The receiving host is under heavy interrupt load. Andrew Gallatin has > :> said to me that this is a classic case of livelock, where the system > :> is so busy processing interrupts that nothing else is getting done. > :> In this case, the NIC is dutifully DMAing all the packets to the host > :> and the driver is queing them all to ether_input(), but this is happening > :... > : > :I think Andrew might be right.. > :it could well be livelock. > : > :Matt Thomas implemented a solution for the 100mb dec cards > :when 100 was fast. I think that the de drivers responded to the > :interrupt and immediatly did SCHEDNETISR() to schedule the rest of > > Hey cool, at least the hardware problem has been solved! > > On the livelock thingy -- well, one way to find out is to use ipfw > to throw away the packets, and then do a 'systat -vm 1' to see where > the cpu's time is being sent and how much cpu is being used. > > I'm guessing between 50% and 70% of the cpu is being eaten with the > packets going into an ipfw bitbucket. > > Each memory read or write represents around 85 MBytes/sec. The DMA counts > as one. The read() system call counts as two ( because it must read from > one memory location and write to another ) -- this puts us perilously > close to the memory bandwidth limit of the cpu when you count all the > other garbage going on that's breaking up the L1 cache. > > :julian > > -Matt > Matthew Dillon > <dillon@backplane.com> > > > > To Unsubscribe: send mail to majordomo@FreeBSD.org > with "unsubscribe freebsd-hackers" in the body of the message To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-hackers" in the body of the message
Want to link to this message? Use this URL: <https://mail-archive.FreeBSD.org/cgi/mid.cgi?199903200606.WAA38098>