Date: Thu, 14 Sep 2006 14:10:37 -0400 From: Kris Kennaway <kris@obsecurity.org> To: Gary Corcoran <gcorcoran@rcn.com> Cc: freebsd-hackers@freebsd.org, Mike Meyer <mwm@mired.org> Subject: Re: numbers don't lie ... Message-ID: <20060914181037.GA55638@xor.obsecurity.org> In-Reply-To: <45099BE3.6080902@rcn.com> References: <E1GNOLq-000DC2-1Q@cs1.cs.huji.ac.il> <863bauk3gp.fsf@dwp.des.no> <45099123.4000500@rcn.com> <17673.37830.1883.272019@bhuda.mired.org> <45099BE3.6080902@rcn.com>
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--opJtzjQTFsWo+cga Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Content-Transfer-Encoding: quoted-printable On Thu, Sep 14, 2006 at 02:13:55PM -0400, Gary Corcoran wrote: > Mike Meyer wrote: > >In <45099123.4000500@rcn.com>, Gary Corcoran <gcorcoran@rcn.com> typed: > >>The confusing thing is that I thought 'real' time should be >=3D 'user'= +=20 > >>'sys'. > >>But here 'user' is much greater than 'real' for both machines! The sen= se=20 > >>I > >>got from the other messages in this thread is that 'user' time is somew= hat > >>meaningless (i.e. unreliable as a measure) in a multi-CPU and/or=20 > >>hyperthreading > >>environment. Can you clarify? > > > >'real' is wall clock time. 'user' and 'sys' are cpu time. If your > >process gets all of some cpu, then user + sys will be the same as real > >time. It's not possible to get more than all of a cpu, so that's a > >maximum *per cpu*. If you have multiple cpus, the formula you want is > >'real' * ncpu >=3D 'user' + 'sys'. >=20 > Thanks to all of you for the responses. The thing that was not clear is > that despite the printed messages, user (and sys) time are *not* measures > of time. Yes they are, they're cumulative amount of time spent executing code in userland or in the kernel. Kris --opJtzjQTFsWo+cga Content-Type: application/pgp-signature Content-Disposition: inline -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.5 (FreeBSD) iD8DBQFFCZscWry0BWjoQKURAmoTAJ9IUXWyMHrayD98p+GjhqwSFwFxDQCgypZB exEb6D4GF5WDAm+SwVaMv3s= =Yqif -----END PGP SIGNATURE----- --opJtzjQTFsWo+cga--
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