Date: Sun, 03 Jun 2007 08:55:53 +0000 From: "Poul-Henning Kamp" <phk@phk.freebsd.dk> To: Nate Lawson <nate@root.org> Cc: takawata@freeBSD.org, Dag-Erling Sm??rgrav <des@des.no>, current@freeBSD.org, Kris Kennaway <kris@obsecurity.org> Subject: Re: HPET vs other timers Message-ID: <49988.1180860953@critter.freebsd.dk> In-Reply-To: Your message of "Sat, 02 Jun 2007 17:30:10 MST." <46620B92.8020608@root.org>
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In message <46620B92.8020608@root.org>, Nate Lawson writes: >Poul-Henning Kamp wrote: >> Nate Lawson wrote: >>>> Anyone able to speculate why though? HPET only reads 32 bits from a >>>> memory mapped region. No locking or other requirements. ACPI_timer >>>> does multiple IO ops, which according to bde@ are much slower than >>>> memory reads. >> >> HPET needs to do metastability mitigation and is not "just a read >> from a memory mapped region". > >If it does, then it's not implemented yet: It's implemented in hardware, that's why the read is so slow. -- 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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