Date: Fri, 26 Sep 2003 12:18:17 +0200 From: Marko Zec <zec@tel.fer.hr> To: Roderick van Domburg <r.s.a.vandomburg@student.utwente.nl> Cc: freebsd-net@freebsd.org Subject: Re: DEVICE_POLLING together with link0 interrupt offloading? Message-ID: <3F741269.3A2FF9FC@tel.fer.hr> References: <000501c3840c$6da6ae60$6ba55982@gog>
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Roderick van Domburg wrote: > Hello everyone, > > Just curious: I just noticed that DEVICE_POLLING works perfectly well with > the interrupt offloading feature of the fxp driver (link0). In my > understanding, both try to improve ``network scheduling'' for lack of better > words - especially under load. Also I now understand that DEVICE_POLLING is > preferred over interrupt offloading, especially on routers. > > But just for the sake of curiosity: what does enabling _both_ bring about to > the network performancy and latency? I'm thinking that latency would be > greatly increased because the poller would often miss the bundled packets. > > What's your take on this? There's no much sense in enabling both the network interface polling mode and fxp interrupt coalescing microcode at the same time, since the polling code disables all network interface interrupts anyway. Moreover, there wouldn't be any additional latency, since the polling routine would extract all incoming packets from inbound DMA rings as soon as they would arrive. Marko
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