Date: Fri, 14 Jan 2011 09:39:36 +0100 (CET) From: sthaug@nethelp.no To: cswiger@mac.com Cc: freebsd-net@freebsd.org Subject: Re: igb watchdog timeouts Message-ID: <20110114.093936.74681829.sthaug@nethelp.no> In-Reply-To: <54D25D8E-ED8C-41E8-BD14-4EB86F4D63C3@mac.com> References: <0B45B324-A819-4230-BBE3-F8468F2DA88F@mac.com> <20110114154326.E27511@besplex.bde.org> <54D25D8E-ED8C-41E8-BD14-4EB86F4D63C3@mac.com>
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> > They have enough buffers (128 for each of tx and rx IIRC). The only thing > > polling mode gave for them was lower latency, but this cost enabling > > polling in the idle loop, which wastes 100% of at least 1 CPU and some > > power. Without polling in idle, polling gives very high latency (even > > worse than low-quality interrupt moderation does). > > Sure-- there are circumstances where a machine would always have traffic to process, for which idle polling was beneficial to enable. I have a couple of servers with Broadcom (bge) GigE interfaces. These servers became completely unresponsive/unusable at high network traffic (presumably due to the interrupt processing) but were able to handle the same traffic with no problems after switching to polling. This was in the 7.0 timeframe. I still have the same servers/interfaces running with polling, but now at 7.3. Steinar Haug, Nethelp consulting, sthaug@nethelp.no
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