Date: Mon, 11 Aug 2008 12:22:33 +0000 (UTC) From: naddy@mips.inka.de (Christian Weisgerber) To: freebsd-net@freebsd.org Subject: Re: Rx/tx hardware checksumming statistics? Message-ID: <g7pau9$2us0$1@lorvorc.mips.inka.de> References: <g7ktnq$glp$1@lorvorc.mips.inka.de> <20080811021703.GC50045@cdnetworks.co.kr>
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Pyun YongHyeon <pyunyh@gmail.com> wrote: > I don't think it indicates whether checksum offloading actually > works as OpenBSD blindly set a flag, which was derived from > hardware, to indicate hardware performed the checksum computation. Yes. It counts the instances where the network stack assumes that the hardware successfully verified the checksum. That is an interesting number. OpenBSD's re(4) driver is ported from FreeBSD. Recently, Brad Smith has been merging the tx/rx checksum offload support for the newer chips (RTL8111C etc.) into the OpenBSD driver and I have done some testing for him. Looking at the counters, I have noticed: * IP header rx checksumming is only registered for IP/TCP and IP/UDP packets, but not for other protocols, such as IP/ICMP. * If VLAN tagging is enabled, no rx checksumming is registered at all. I don't have documentation for the Realtek chips, so I don't know if the hardware really cannot perform these operations or if the driver simply fails to take advantage of them. Presumably the same limitations also apply to the FreeBSD driver, but without the counters, how can you tell? -- Christian "naddy" Weisgerber naddy@mips.inka.de
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