Date: Thu, 04 Apr 2002 15:46:42 -0800 From: Terry Lambert <tlambert2@mindspring.com> To: Andrew Gallatin <gallatin@cs.duke.edu> Cc: Will Froning <wfroning@angui.sh>, hackers@freebsd.org Subject: Re: Fatal trap 12: page fault while in kernel mode Message-ID: <3CACE5E2.7C20E5BB@mindspring.com> References: <20020403181854.I42720-100000@angui.sh> <15532.29114.310072.957330@grasshopper.cs.duke.edu>
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Andrew Gallatin wrote: > While the fix being discussed by Peter & others will prevent panics, > the linux box will still run your server out of mbufs clusters. This > is happening because the linux box is using a 16K write size over UDP > by default. This is a stupid default. If there is any lossage > between the hosts (eg, any packets get dropped), more and more packets > will end up on the reassembly queues. Eventually, all your cluster > mbufs will be there. > > I suggest changing the mount options on the linux box to use 8k reads > and writes, or use TCP. Good observation. Actually, for a firewall box, it might be reasonable to drop UDP packets over a certain size, and to drop certain classes of frags. This won't help the original poster with the Linux problem; they would still have to reconfigure their Linux machine to use smaller writes. > Another problem I've see w/Linux NFS clients is that recent linux NFS > clients seem to spew ACCESS requests like there's no tomorrow & beats > the snot out of my NFS server. When building large software pacakges > via "make -j4" over NFSv3 (100Mb ethernet) on a dual PIII 1GHz system, > a FreeBSD 4.5 host issues 400-500 ACCESS calls/sec. A Linux 2.4.18 > host spews 12,000 - 14,000 ACCESS calls/sec, or roughly 30 times as > many. Needless to say, the build finishes a whole lot quicker on > FreeBSD. Does anybody know what I can do to make the linux client > cache ACCESS info? Apart from installing FreeBSD instead? 8-). I think that it will take some hacking of the Linux NFS code by someone who cares about Linux performance. -- Terry To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-hackers" in the body of the message
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