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Date:      Thu, 31 May 2012 16:37:31 +0200
From:      Fabian Keil <freebsd-listen@fabiankeil.de>
To:        Ryan Stone <rysto32@gmail.com>
Cc:        freebsd-hackers@freebsd.org, Chadd <adrian@freebsd.org>, Alexander Motin <mav@freebsd.org>, Andriy Gapon <avg@freebsd.org>, Adrian
Subject:   Re: ULE/sched issues on stable/9 - why isn't preemption occuring?
Message-ID:  <20120531163731.364570cc@fabiankeil.de>
In-Reply-To: <CAFMmRNyLoA3ayfVjrEzU5wLpfwWaYU7yM7V9Ns0r0nrCTYmTXg@mail.gmail.com>
References:  <CAJ-VmomWV2XibSNSr5Mfh7mpKsWrX5GKsNfU9iq7TO6%2BKxxQhw@mail.gmail.com> <201205301124.52597.jhb@freebsd.org> <CAJ-VmokXN9Ci8j2ExZkA-U=fsrMmeOn-ULB0pCYdtSwqHWpiKQ@mail.gmail.com> <CAJ-VmomU8mK5W%2BKrj4Mtn=3R=EcqPB-YDd9LwNxZo49%2By96bzA@mail.gmail.com> <4FC76515.10302@FreeBSD.org> <CAFMmRNyLoA3ayfVjrEzU5wLpfwWaYU7yM7V9Ns0r0nrCTYmTXg@mail.gmail.com>

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Ryan Stone <rysto32@gmail.com> wrote:

> On Thu, May 31, 2012 at 8:33 AM, Andriy Gapon <avg@freebsd.org> wrote:
> > In this vein it might make sense to enable KTR and KTR_SCHED in GENERIC.
>=20
> KTR_SCHED comes with a performance hit.  Besides, with the DTrace
> sched provider that I committed this month (and MFC'ed yesterday) you
> can collect schedgraph data with a D script.

Unfortunately DTrace's timestamp itself doesn't always
work reliably on FreeBSD, and schedgraph.d depends on it.

On my system DTrace's timestamp seems to work with
kern.timecounter.hardware=3DHPET and dev.cpu.0.cx_lowest=3DC2
(or C1) but seems to tick much too slow with dev.cpu.0.cx_lowest=3DC3:
http://lists.freebsd.org/pipermail/freebsd-current/2011-August/026710.html

Fabian

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