Date: Mon, 31 Dec 2012 07:58:52 -0800 From: Garrett Cooper <yanegomi@gmail.com> To: Barney Cordoba <barney_cordoba@yahoo.com> Cc: freebsd-net@freebsd.org, David Christensen <davidch@freebsd.org>, linimon@freebsd.org Subject: Re: kern/174851: [bxe] [patch] UDP checksum offload is wrong in bxe driver Message-ID: <CAGH67wSRdvWMRqU_SgFYNp6jPRohig%2BcrWDjem_BBXpKOTXqtw@mail.gmail.com> In-Reply-To: <1356969238.85857.YahooMailClassic@web121602.mail.ne1.yahoo.com> References: <201212310728.qBV7SPKC064686@freefall.freebsd.org> <1356969238.85857.YahooMailClassic@web121602.mail.ne1.yahoo.com>
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On Mon, Dec 31, 2012 at 7:53 AM, Barney Cordoba <barney_cordoba@yahoo.com> wrote: ... > Has anyone done an analysis on modern hardware as to whether udp csum > offloading is actually beneficial? Even on 2007 hardware I came to the > conclusion that using offloading was a negative. > > Reminds me of the days when people were using "intelligent" ethernet cards > that were slower than the host cpu. The handshaking cost you more than > just using shared memory. I would ask David about whether or not there was a performance difference because they might have some numbers for if_bxe. Not sure about the concept in general, but it seems like a reasonable application protocol specific request. But by and large, I agree that UDP checksumming doesn't make logical sense because it adds unnecessary overhead on a L3 protocol that's assumed to be unreliable. Thanks, -Garrett
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