Date: Tue, 1 Jul 2008 12:31:18 +0900 From: Pyun YongHyeon <pyunyh@gmail.com> To: Sepherosa Ziehau <sepherosa@gmail.com> Cc: freebsd-net@freebsd.org, "Support \(Rudy\)" <crapsh@monkeybrains.net>, "Wilkinson, Alex" <alex.wilkinson@dsto.defence.gov.au>, Ingo Flaschberger <if@xip.at>, Paul <paul@gtcomm.net> Subject: Re: Freebsd IP Forwarding performance (question, and some info) [7-stable, current, em, smp] Message-ID: <20080701033117.GH83626@cdnetworks.co.kr> In-Reply-To: <ea7b9c170806302005n2a66f592h2127f87a0ba2c6d2@mail.gmail.com> References: <4867420D.7090406@gtcomm.net> <200806301944.m5UJifJD081781@lava.sentex.ca> <20080701004346.GA3898@stlux503.dsto.defence.gov.au> <alpine.LFD.1.10.0807010257570.19444@filebunker.xip.at> <20080701010716.GF3898@stlux503.dsto.defence.gov.au> <alpine.LFD.1.10.0807010308320.19444@filebunker.xip.at> <486986D9.3000607@monkeybrains.net> <48699960.9070100@gtcomm.net> <ea7b9c170806302005n2a66f592h2127f87a0ba2c6d2@mail.gmail.com>
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On Tue, Jul 01, 2008 at 11:05:03AM +0800, Sepherosa Ziehau wrote: > On 7/1/08, Paul <paul@gtcomm.net> wrote: > > All the NIC drivers in 7 pretty much use interrupt moderation so it can > > I am not quite sure whether em(4)'s RX interrupt moderation works as > expected or not. But, AFAIK, nfe(4) and re(4) does not have RX > interrupt moderation. Their TX interrupt moderation could be mimiced > by using their hardware timer and disabling their TX interrupt. > > The lacking of RX im is difficult to handle, I could imagine following way: > - During init, enable RX intr > - When RX intr comes, disable RX intr and set up hardware timer intr > - When timer intr comes and no RX happens, disable timer intr and enable RX intr > I guess adaptive polling would give the same effect withtout sacrificing CPU cycles. > Properly configured #RX desc and timer intr interval will be required > to make sure that the RX desc collection could keep up with the > hardware speed. I used pure timer intr (8000Hz) on nfe(4) in dfly w/ > good result, i.e. TX/RX @linespeed without livelocking the system. I thought that too for a while but I prefer to hardware intertrrupt moderation feature. Of course I still have no clue how to enable that interrupt feature on nvidia controllers. :-( > The drawback of pure timer intr is that you waste extra cpu power, > when there is nothing to process. > > > never lock the machine anyway.. This effectively kills polling and it really > > no longer has any use except to be able to have a fraction of the cpu set > > Oh? Really? :] > > Best Regards, > sephe > > -- > Live Free or Die -- Regards, Pyun YongHyeon
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