Date: Wed, 29 Apr 2015 10:06:58 -0400 From: Garrett Wollman <wollman@bimajority.org> To: Mark Schouten <mark@tuxis.nl> Cc: freebsd-net@FreeBSD.org Subject: Re: Frequent hickups on the networking layer Message-ID: <21824.58754.452182.195043@hergotha.csail.mit.edu> In-Reply-To: <5540889A.5030904@tuxis.nl> References: <137094161.27589033.1430255162390.JavaMail.root@uoguelph.ca> <5540889A.5030904@tuxis.nl>
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<<On Wed, 29 Apr 2015 09:30:34 +0200, Mark Schouten <mark@tuxis.nl> said: > I'm not really (or really not) comfortable with hacking and recompiling > stuff. I'd rather not change anything in the kernel. So would it help in > my case to lower my MTU from 9000 to 4000? If I understand correctly, > this would need to allocate chunks of 4k, which is far more logical from > a memory point of view? If you're using one of the drivers that has this problem, then yes, keeping your layer-2 MTU/MRU below 4096 will probably cause it to use 4k (page-sized) clusters instead, which are perfectly safe. As a side note, at least on the hardware I have to support, Infiniband is limited to 4k MTU -- so I have one "jumbo" network with 4k frames (that's bridged to IB) and one with 9k frames (that everything else uses). -GAWollman
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