Date: Sat, 31 Jul 2021 15:48:31 +0300 From: Konstantin Belousov <kostikbel@gmail.com> To: Alexander Motin <mav@freebsd.org> Cc: src-committers@freebsd.org, dev-commits-src-all@freebsd.org, dev-commits-src-main@freebsd.org Subject: Re: git: 74f80bc1af2f - main - coretemp(4): Switch to smp_rendezvous_cpus(). Message-ID: <YQVGn7VhKstcGndr@kib.kiev.ua> In-Reply-To: <202107300326.16U3QGHR070204@gitrepo.freebsd.org> References: <202107300326.16U3QGHR070204@gitrepo.freebsd.org>
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On Fri, Jul 30, 2021 at 03:26:16AM +0000, Alexander Motin wrote: > The branch main has been updated by mav: > > URL: https://cgit.FreeBSD.org/src/commit/?id=74f80bc1af2ffd56ec290f610c80e46f768731a0 > > commit 74f80bc1af2ffd56ec290f610c80e46f768731a0 > Author: Alexander Motin <mav@FreeBSD.org> > AuthorDate: 2021-07-30 03:16:22 +0000 > Commit: Alexander Motin <mav@FreeBSD.org> > CommitDate: 2021-07-30 03:26:10 +0000 > > coretemp(4): Switch to smp_rendezvous_cpus(). > > Use of smp_rendezvous_cpus() instead of sched_bind() allows to not > block indefinitely if target CPU is running some thread with higher > priority, while all we need is single rdmsr/wrmsr instruction call. > I guess it should also be much cheaper than full thread migration. > > MFC after: 2 weeks > Sponsored by: iXsystems, Inc. > --- > sys/dev/coretemp/coretemp.c | 59 ++++++++++++++++++++++++++++----------------- > 1 file changed, 37 insertions(+), 22 deletions(-) > > diff --git a/sys/dev/coretemp/coretemp.c b/sys/dev/coretemp/coretemp.c > index 884ed6309f0e..53a2434254f6 100644 > --- a/sys/dev/coretemp/coretemp.c > +++ b/sys/dev/coretemp/coretemp.c > @@ -42,7 +42,7 @@ __FBSDID("$FreeBSD$"); > #include <sys/module.h> > #include <sys/mutex.h> > #include <sys/proc.h> /* for curthread */ > -#include <sys/sched.h> > +#include <sys/smp.h> > #include <sys/sysctl.h> > #include <sys/systm.h> > > @@ -310,14 +310,32 @@ coretemp_detach(device_t dev) > return (0); > } > > +struct coretemp_args { > + u_int msr; > + uint64_t val; > +}; > + > +static void > +coretemp_rdmsr(void *arg) > +{ > + struct coretemp_args *args = arg; > + > + args->val = rdmsr(args->msr); > +} > + > +static void > +coretemp_wrmsr(void *arg) > +{ > + struct coretemp_args *args = arg; > + > + wrmsr(args->msr, args->val); > +} We have x86_msr_op(). It covers coretemp_wrmsr(), and with slight change of the interface would also handle the functionality of coretemp_rdmsr(). > + > static uint64_t > coretemp_get_thermal_msr(int cpu) > { > - uint64_t msr; > - > - thread_lock(curthread); > - sched_bind(curthread, cpu); > - thread_unlock(curthread); > + struct coretemp_args args; > + cpuset_t cpus; > > /* > * The digital temperature reading is located at bit 16 > @@ -329,27 +347,24 @@ coretemp_get_thermal_msr(int cpu) > * The temperature is computed by subtracting the temperature > * reading by Tj(max). > */ > - msr = rdmsr(MSR_THERM_STATUS); > - > - thread_lock(curthread); > - sched_unbind(curthread); > - thread_unlock(curthread); > - > - return (msr); > + args.msr = MSR_THERM_STATUS; > + CPU_SETOF(cpu, &cpus); > + smp_rendezvous_cpus(cpus, smp_no_rendezvous_barrier, coretemp_rdmsr, > + smp_no_rendezvous_barrier, &args); > + return (args.val); > } > > static void > coretemp_clear_thermal_msr(int cpu) > { > - thread_lock(curthread); > - sched_bind(curthread, cpu); > - thread_unlock(curthread); > - > - wrmsr(MSR_THERM_STATUS, 0); > - > - thread_lock(curthread); > - sched_unbind(curthread); > - thread_unlock(curthread); > + struct coretemp_args args; > + cpuset_t cpus; > + > + args.msr = MSR_THERM_STATUS; > + args.val = 0; > + CPU_SETOF(cpu, &cpus); > + smp_rendezvous_cpus(cpus, smp_no_rendezvous_barrier, coretemp_wrmsr, > + smp_no_rendezvous_barrier, &args); > } > > static int
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