Date: Sat, 20 Sep 2003 13:00:54 -0700 (PDT) From: John Polstra <jdp@polstra.com> To: Luigi Rizzo <rizzo@icir.org> Cc: freebsd-arch@freebsd.org Subject: Re: interrupt latency and driver locking Message-ID: <XFMail.20030920130054.jdp@polstra.com> In-Reply-To: <20030920100911.B55993@xorpc.icir.org>
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On 20-Sep-2003 Luigi Rizzo wrote: > the main problem, as i see it, is that when there are PHY events you > still need to do some expensive work while holding a lock that > blocks interrupts, with very bad impact on the worst-case > response of the system. I agree that is a problem, but I don't think it is the main problem. In a running system, PHY events essentially never happen, so it doesn't matter much if they take a long time. In other words, the PHY really only needs attention when the link state changes, and for all practical purposes that never happens in a running system. What is killing us is the periodic polling of the PHY every second, only to find out that nothing has changed. John
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