Date: Thu, 12 Feb 2004 09:26:16 -0500 (EST) From: Andrew Gallatin <gallatin@cs.duke.edu> To: Dung Patrick <dkt@digitalme.com> Cc: freebsd-hackers@freebsd.org Subject: Re: Zero copy sockets question Message-ID: <16427.36104.975516.452339@grasshopper.cs.duke.edu> In-Reply-To: <1076577152.c8c39c40dkt@digitalme.com> References: <1076577152.c8c39c40dkt@digitalme.com>
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Dung Patrick writes: > Hi > > I have read http://people.freebsd.org/~ken/zero_copy/ > > To correctly use zero copy receive, it seems it need to set the MTU to: > have to be at least page sized, and be aligned on page boundaries. Yes. > So is the default MTU for ethernet network card 1500 works? No, you need to have an MTU of at least PAGE_SIZE + headers. And a NIC which is smart enough to do the header splitting. Currently, the Alteon Tigon2 is the only nic which fits the bill. I keep meaning to implement header splitting in the Myricom Myrinet firmware, and I keep not getting time for it.. Note that send-side zero-copy works on any NIC, and with a standard MTU. Drew
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