Date: Fri, 14 Oct 2005 21:36:28 +0200 From: "Poul-Henning Kamp" <phk@phk.freebsd.dk> To: Andrew Gallatin <gallatin@cs.duke.edu> Cc: Garrett Wollman <wollman@csail.mit.edu>, net@FreeBSD.org Subject: Re: Call for performance evaluation: net.isr.direct (fwd) Message-ID: <33011.1129318588@critter.freebsd.dk> In-Reply-To: Your message of "Fri, 14 Oct 2005 15:19:19 EDT." <17232.1207.615226.432579@grasshopper.cs.duke.edu>
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In message <17232.1207.615226.432579@grasshopper.cs.duke.edu>, Andrew Gallatin writes: > >Poul-Henning Kamp writes: > > The solution is not faster but less reliable timekeeping, the > > solution is to move the scheduler(s) away from using time as an > > approximation of cpu cycles. > >So you mean rather than use binuptime() in mi_switch(), use some >per-cpu cycle counter (like rdtsc)? yes. >Heck, why not just use ticks for the scheduler and keep the expensive >timekeeping code out of the critical path altogether? Does it really >need better than 1ms resolution? Because the resource accounting needs to know how much cpu power each process/thread has used, and the units used assume a constant clockrate (see times(3)) -- Poul-Henning Kamp | UNIX since Zilog Zeus 3.20 phk@FreeBSD.ORG | TCP/IP since RFC 956 FreeBSD committer | BSD since 4.3-tahoe Never attribute to malice what can adequately be explained by incompetence.
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