Date: Wed, 14 Jun 2006 11:38:47 -0400 From: Kris Kennaway <kris@obsecurity.org> To: John Baldwin <jhb@freebsd.org> Cc: freebsd-current@freebsd.org, Robert Watson <rwatson@freebsd.org>, John Birrell <jb@what-creek.com>, current@freebsd.org Subject: Re: DTrace for FreeBSD - fbt output Message-ID: <20060614153846.GA37259@xor.obsecurity.org> In-Reply-To: <200606141021.45669.jhb@freebsd.org> References: <20060613021543.GA71283@what-creek.com> <20060614103614.Y34121@fledge.watson.org> <20060614095449.GA82424@what-creek.com> <200606141021.45669.jhb@freebsd.org>
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--9amGYk9869ThD9tj Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Content-Transfer-Encoding: quoted-printable On Wed, Jun 14, 2006 at 10:21:44AM -0400, John Baldwin wrote: > On Wednesday 14 June 2006 05:54, John Birrell wrote: > > > > critical_enter 4364385478 > > > > critical_exit 4364385478 > >=20 > > The points I wanted to make about these calls are: > >=20 > > 1. critical_enter is called so often that the debug printf that /could/ > > be compiled into it should cause an increase in global warming if > > you tried. 8-) >=20 > No, it's not a printf to the console it's a printf into the a circular > buffer (see options KTR) and the system has been run with it enabled w/o > burning the machine up. :) For point of comparison, I added an implementation of spinlock profiling in my kris-contention p4 branch which does a KTR every 100 mtx_lock_spin() operations, and this has less than 5% performance impact. KTR is very cheap since it is just a single atomic op to increment the buffer index, and then a couple of pointer assignments. Kris --9amGYk9869ThD9tj Content-Type: application/pgp-signature Content-Disposition: inline -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.3 (FreeBSD) iD8DBQFEkC2GWry0BWjoQKURAhG6AJ4l6g7QlubMs4H4k/Jk/GKYLkFK+gCdExNH ByNmdl4Grn9GJ1TjU0DYhpg= =sH1V -----END PGP SIGNATURE----- --9amGYk9869ThD9tj--
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