Date: Fri, 18 Apr 2008 06:00:08 +0000 From: "Poul-Henning Kamp" <phk@phk.freebsd.dk> To: Julian Elischer <julian@elischer.org> Cc: gnn@freebsd.org, freebsd-current@freebsd.org, Andrew Gallatin <gallatin@cs.duke.edu> Subject: Re: TSC Timecounter and multi-core/SMP Message-ID: <51610.1208498408@critter.freebsd.dk> In-Reply-To: Your message of "Thu, 17 Apr 2008 19:07:50 MST." <48080276.3040203@elischer.org>
next in thread | previous in thread | raw e-mail | index | archive | help
In message <48080276.3040203@elischer.org>, Julian Elischer writes: >David O'Brien wrote: > >> >> The TSC on K8 is not invariant - its rate of change is affected by >> P-state changes. >> >> The TSC on Greyhound (Family 10h) is invariant. >> [but as stated above, is not synced with other cores] > >You'd think that an invariant sync'd clock (fast to read) of some >type would have been done by someone by now.. The software people >have been asking for this for the last decade at least. Actually one of the original design documents for SAGE stressed that such hardware were crucially important "for any system operating in real time", so yes, the HW people have had adequate notices. Poul-Henning -- 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.
Want to link to this message? Use this URL: <https://mail-archive.FreeBSD.org/cgi/mid.cgi?51610.1208498408>