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Date: Fri, 24 Apr 2009 10:13:52 -0700 From: Rick Jones <rick.jones2@...com> To: Andrew Gallatin <gallatin@...i.com> CC: Herbert Xu <herbert@...dor.apana.org.au>, David Miller <davem@...emloft.net>, brice@...i.com, sgruszka@...hat.com, netdev@...r.kernel.org Subject: Re: [PATCH] myr10ge: again fix lro_gen_skb() alignment > This is strange. I wonder if it might be a cache footprint issue? > My intentionally weak receiver is an athlon64 x2 "Toledo", and > has only 512KB L2 cache. I can re-test with a core-2 based Xeon. A point about netperf :) By default, it will use one more buffer than the initial size of the socket buffer divided by the send/recv buffer size - this goes back to days of copy-avoidance, a flavor of which can be found in reading: ftp://ftp.cup.hp.com/dist/networking/briefs/copyavoid.pdf particularly section 3.2. It can be overridden with the global -W option: -W send,recv Set the number of send,recv buffers Of course, this will interact with other things such as: The default send/recv size will be the send/recv socket buffer size. That can be overridden with the test-specific -m/-M options. The default socket buffer size will be whatever the system gives it. That can be overridden with the test-specific -s/-S options. So, the various options can have a non-trivial effect on the cache footprint of the data netperf is shoving around. rick jones -- To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
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