Date: Thu, 10 Sep 2009 23:02:19 +0930 From: "Daniel O'Connor" <doconnor@gsoft.com.au> To: freebsd-stable@freebsd.org Cc: Luigi Rizzo <rizzo@iet.unipi.it>, John Baldwin <jhb@freebsd.org> Subject: Re: incorrect usleep/select delays with HZ > 2500 Message-ID: <200909102302.26318.doconnor@gsoft.com.au> In-Reply-To: <200909091642.06046.jhb@freebsd.org> References: <20090906155154.GA8283@onelab2.iet.unipi.it> <20090909203216.GA93761@onelab2.iet.unipi.it> <200909091642.06046.jhb@freebsd.org>
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--nextPart1480948.AHEMIzcntJ Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable Content-Disposition: inline On Thu, 10 Sep 2009, John Baldwin wrote: > > $ARCH/isa/clock.c::DELAY(). I suppose with a few measurements > > at different HZ values and some back of the envelope calculations > > one could even determine estimate the frequency and duration > > of those SMI interrupts! > > On recent motherboards I have seen the SMI# interrupt fire every 250 > ms with execution times ranging from 50 us to 1ms for the legacy USB > interrupt handler. We consistently see the TSC frequency > miscalculated on the motherboards with the 1ms duration interrupt. I > suspect that the clock that drives the periodic SMI# interrupt is > tied to the i8254 meaning that it often fires at the same time that > the i8254 wraps causing the TSC frequency to often be wrong. Can the calculation code disable the SMI# interrupt? Disabling legacy=20 USB could be a problem if you want to use a USB keyboard with the=20 loader (I think). =2D-=20 Daniel O'Connor software and network engineer for Genesis Software - http://www.gsoft.com.au "The nice thing about standards is that there are so many of them to choose from." -- Andrew Tanenbaum GPG Fingerprint - 5596 B766 97C0 0E94 4347 295E E593 DC20 7B3F CE8C --nextPart1480948.AHEMIzcntJ Content-Type: application/pgp-signature; name=signature.asc Content-Description: This is a digitally signed message part. -----BEGIN PGP SIGNATURE----- Version: GnuPG v2.0.12 (FreeBSD) iD8DBQBKqP/q5ZPcIHs/zowRApbKAJ0Y8SHe6RVNNgKBWgeWlQ0MY4L6zACfelI6 ugYVtZytpigqEj9XR/2ICpE= =dhSe -----END PGP SIGNATURE----- --nextPart1480948.AHEMIzcntJ--
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