Date: Mon, 17 Mar 2008 09:42:52 -0500 From: Brooks Davis <brooks@freebsd.org> To: John Baldwin <jhb@freebsd.org> Cc: freebsd-arch@freebsd.org Subject: Re: [PATCH] hwpmc(4) changes to use 'mp_maxid' instead of 'mp_ncpus'. Message-ID: <20080317144251.GA38485@lor.one-eyed-alien.net> In-Reply-To: <200803170947.25205.jhb@freebsd.org> References: <20080313180805.GA83406@dragon.NUXI.org> <200803141431.53846.jhb@freebsd.org> <84dead720803142243r6c8cc68dm325e7fb925189fd@mail.gmail.com> <200803170947.25205.jhb@freebsd.org>
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--82I3+IH0IqGh5yIs Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Content-Transfer-Encoding: quoted-printable On Mon, Mar 17, 2008 at 09:47:25AM -0400, John Baldwin wrote: > On Saturday 15 March 2008 01:43:00 am Joseph Koshy wrote: > > > FreeBSD has been trying to not be quite as i386-centric as it used to > > > be. If you look at other code in the kernel that handles per-cpu data > > > such as UMA you will see that it uses mp_maxid and CPU_ABSENT(). The= re > > > are other places in the kernel that are broken though (such as ndis(4= )). > > > > HWPMC is very x86 centric, for obvious reasons. >=20 > Considering other CPU archictectures support various performance counters= it=20 > really shouldn't be designed to be x86-centric even if it is currently on= ly=20 > implemented for x86 CPUs. We should take some care to make sure we don't over generalize. From what I've heard the people who wrote the performance counter framework for x86 in linux where very, very unhappy when told to rework everything to support at framework that went with ia64's exponentionaly more complex instrumentation. If we can make small changes to support more conventional non-x86 platforms, that's probably a good idea. If nothing else, these counters could be even more useful on CPU-poor embedded devices. -- Brooks --82I3+IH0IqGh5yIs Content-Type: application/pgp-signature Content-Disposition: inline -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.8 (FreeBSD) iD8DBQFH3oNrXY6L6fI4GtQRAjbYAKC+QcDLzwdkxSwfiHwvcfSLL7iOOgCgidXe juBHKIAfKToVaSnCGmVsI4Y= =99LI -----END PGP SIGNATURE----- --82I3+IH0IqGh5yIs--
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