Date: Mon, 07 Apr 2003 00:03:59 +0200 From: "Poul-Henning Kamp" <phk@phk.freebsd.dk> To: Dag-Erling Smorgrav <des@ofug.org> Cc: Nate Lawson <nate@root.org> Subject: Re: cvs commit: src/sys/conf options.i386 src/sys/i386/i386 tsc.c src/sys/i386/conf NOTES Message-ID: <30949.1049666639@critter.freebsd.dk> In-Reply-To: Your message of "Sun, 06 Apr 2003 23:32:40 %2B0200." <xzpof3js45j.fsf@flood.ping.uio.no>
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In message <xzpof3js45j.fsf@flood.ping.uio.no>, Dag-Erling Smorgrav writes: >--=-=-= > >Nate Lawson <nate@root.org> writes: >> Perhaps you could enable this option by default if it had a corresponding >> check for drift that would disable it if things got out of hand. > >There wouldn't be much point in that unless the SMP_TSC option also >forced the TSC to be selected at boot time. On most SMP systems, the >PIIX timecounter is automatically selected by virtue of being >discovered last. It is specifically discovered last because it should be used if at all possible. >I must have bad benchmark karma, BTW - I can see no reduction of >context switch time or any other significant performance boost when >using the TSC on my dual Celeron system. There is a big difference if you get to use "ACPI-fast" (correctly implemented hardware) instead of "ACPI-safe" (buggy hardware). -- 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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