Date: Tue, 24 Apr 2012 17:05:24 +0200 From: "K. Macy" <kmacy@freebsd.org> To: "Li, Qing" <qing.li@bluecoat.com> Cc: Luigi Rizzo <rizzo@iet.unipi.it>, "current@freebsd.org" <current@freebsd.org>, "net@freebsd.org" <net@freebsd.org> Subject: Re: Some performance measurements on the FreeBSD network stack Message-ID: <CAHM0Q_NWbDMHycyX7-Upv4zQ%2B7W2Qe1fMd%2BnReoEENJ0KgwmsQ@mail.gmail.com> In-Reply-To: <CAHM0Q_OQUJ0E6kPXkPTh0LEYP8yCJjfW8Z_NZ5d-cKyaHW-8AQ@mail.gmail.com> References: <20120419133018.GA91364@onelab2.iet.unipi.it> <4F907011.9080602@freebsd.org> <20120419204622.GA94904@onelab2.iet.unipi.it> <4F96A7C0.3010909@freebsd.org> <20120424140228.GA58809@onelab2.iet.unipi.it> <B143A8975061C446AD5E29742C531723C7C16A@pwsvl-excmbx-05.internal.cacheflow.com> <CAHM0Q_OQUJ0E6kPXkPTh0LEYP8yCJjfW8Z_NZ5d-cKyaHW-8AQ@mail.gmail.com>
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On Tue, Apr 24, 2012 at 5:03 PM, K. Macy <kmacy@freebsd.org> wrote: > On Tue, Apr 24, 2012 at 4:16 PM, Li, Qing <qing.li@bluecoat.com> wrote: >>> >> >From previous tests, the difference between flowtable and >>>routing table was small with a single process (about 5% or 50ns >>>in the total packet processing time, if i remember well), >>>but there was a large gain with multiple concurrent processes. >>> >> >> Yes, that sounds about right when we did the tests a long while ago. >> >>> >>> Removing flowtable increases the cost in ip_output() >>> (obviously) but also in ether_output() (because the >>> route does not have a lle entry so you need to call >>> arpresolve on each packet). >>> >> >> Yup. >> >>> >>> So in revising the route lookup i believe it would be good >>> if we could also get at once most of the info that >>> ether_output() is computing again and again. >>> >> >> Well, the routing table no longer maintains any lle info, so there >> isn't much to copy out the rtentry at the completion of route >> lookup. >> >> If I understood you correctly, you do believe there is a lot of value >> in Flowtable caching concept, but you are not suggesting we reverting >> back to having the routing table maintain L2 entries, are you ? >> > > > One could try a similar conversion of the L2 table to an rmlock > without copy while lock is held. Odd .. *with* copy while lock is held. -Kip
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