Date: Wed, 29 Apr 2009 19:54:17 +0300 From: Kostik Belousov <kostikbel@gmail.com> To: Jeff Roberson <jeff@freebsd.org> Cc: svn-src-head@freebsd.org, svn-src-all@freebsd.org, src-committers@freebsd.org Subject: Re: svn commit: r191643 - in head/sys: kern sys Message-ID: <20090429165417.GG40751@deviant.kiev.zoral.com.ua> In-Reply-To: <200904290315.n3T3FiJW067558@svn.freebsd.org> References: <200904290315.n3T3FiJW067558@svn.freebsd.org>
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--7fVr/IRGAG9sAW4J Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Content-Transfer-Encoding: quoted-printable On Wed, Apr 29, 2009 at 03:15:44AM +0000, Jeff Roberson wrote: > Author: jeff > Date: Wed Apr 29 03:15:43 2009 > New Revision: 191643 > URL: http://svn.freebsd.org/changeset/base/191643 >=20 > Log: > - Remove the bogus idle thread state code. This may have a race in it > and it only optimized out an ipi or mwait in very few cases. > - Skip the adaptive idle code when running on SMT or HTT cores. This > just wastes cpu time that could be used on a busy thread on the same > core. > - Rename CG_FLAG_THREAD to CG_FLAG_SMT to be more descriptive. Re-use > CG_FLAG_THREAD to mean SMT or HTT. > =20 > Sponsored by: Nokia >=20 > Modified: > head/sys/kern/sched_ule.c > head/sys/kern/subr_smp.c > head/sys/sys/smp.h Now I see a reason why it is better #ifdef SMP the code that uses CG_FLAG_*. Also, we should check for tdq_cg !=3D NULL in one more place. See the patch below, instead of exposing CG_FLAG_* for !SMP configs. diff --git a/sys/kern/sched_ule.c b/sys/kern/sched_ule.c index 680572d..fe3a119 100644 --- a/sys/kern/sched_ule.c +++ b/sys/kern/sched_ule.c @@ -891,6 +891,7 @@ tdq_move(struct tdq *from, struct tdq *to) return (1); } =20 +#ifdef SMP /* * This tdq has idled. Try to steal a thread from another cpu and switch * to it. @@ -947,6 +948,7 @@ tdq_idled(struct tdq *tdq) spinlock_exit(); return (1); } +#endif =20 /* * Notify a remote cpu of new work. Sends an IPI if criteria are met. @@ -2525,7 +2527,9 @@ sched_idletd(void *dummy) struct thread *td; struct tdq *tdq; int switchcnt; +#ifdef SMP int i; +#endif =20 mtx_assert(&Giant, MA_NOTOWNED); td =3D curthread; @@ -2543,7 +2547,9 @@ sched_idletd(void *dummy) * loops while on SMT machines as this simply steals * cycles from cores doing useful work. */ - if ((tdq->tdq_cg->cg_flags & CG_FLAG_THREAD) =3D=3D 0 && +#ifdef SMP + if (tdq->tdq_cg !=3D NULL && + (tdq->tdq_cg->cg_flags & CG_FLAG_THREAD) =3D=3D 0 && switchcnt > sched_idlespinthresh) { for (i =3D 0; i < sched_idlespins; i++) { if (tdq->tdq_load) @@ -2551,6 +2557,7 @@ sched_idletd(void *dummy) cpu_spinwait(); } } +#endif switchcnt =3D tdq->tdq_switchcnt + tdq->tdq_oldswitchcnt; if (tdq->tdq_load =3D=3D 0) cpu_idle(switchcnt > 1); --7fVr/IRGAG9sAW4J Content-Type: application/pgp-signature Content-Disposition: inline -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.9 (FreeBSD) iEYEARECAAYFAkn4hjgACgkQC3+MBN1Mb4hsoACfVDIzV4KqZR5Zi/scpiolmWf6 L/UAn0dGosIBRmlW16kn/07cNChsla6g =MG++ -----END PGP SIGNATURE----- --7fVr/IRGAG9sAW4J--
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