PERFORCE change 100121 for review

[John Baldwin]

On Tuesday 27 June 2006 12:31, Kip Macy wrote:
> Point me at your tree. I do :-).
> 
>                      -Kip

Heh.  The tree is at //depot/user/jhb/lock/...  I can also just generate a 
diff if you'd prefer.

> On 6/27/06, John Baldwin <jhb at freebsd.org> wrote:
> > On Tuesday 27 June 2006 03:42, Kip Macy wrote:
> > > http://perforce.freebsd.org/chv.cgi?CH=100121
> > >
> > > Change 100121 by kmacy at kmacy_storage:sun4v_work_sleepq on 2006/06/27
> > 07:41:14
> > >
> > >       avoid pointless turnstile contention if mutex owner is running
> >
> > Yes, I did this already in jhb_lock for both mutexes and rwlocks at 
BSDCan.
> > Kris said my patch panic'd for him at BSDCan but I don't have an SMP 
machine
> > I can test it on now to debug it. :(
> >
> > >
> > > Affected files ...
> > >
> > > .. //depot/projects/kmacy_sun4v/src/sys/kern/kern_mutex.c#20 edit
> > >
> > > Differences ...
> > >
> > > ==== //depot/projects/kmacy_sun4v/src/sys/kern/kern_mutex.c#20 (text+ko)
> > ====
> > >
> > > @@ -176,7 +176,7 @@
> > >  static int mutex_prof_maxrecords = MPROF_HASH_SIZE;
> > >  SYSCTL_INT(_debug_mutex_prof, OID_AUTO, maxrecords, CTLFLAG_RD,
> > >      &mutex_prof_maxrecords, 0, "Maximum number of profiling records");
> > > -int mutex_prof_rejected;
> > > +int mutex_prof_rejected = 0;
> > >  SYSCTL_INT(_debug_mutex_prof, OID_AUTO, rejected, CTLFLAG_RD,
> > >      &mutex_prof_rejected, 0, "Number of rejected profiling records");
> > >  static int mutex_prof_hashsize = MPROF_HASH_SIZE;
> > > @@ -418,6 +418,16 @@
> > >
> > >       while (!_obtain_lock(m, tid)) {
> > >               lock_profile_obtain_lock_failed(&m->mtx_object, 
&contested);
> > > +#if defined(SMP) && !defined(NO_ADAPTIVE_MUTEXES)
> > > +             /*
> > > +              * If the current owner of the lock is executing on 
another
> > > +              * CPU, spin instead of blocking.
> > > +              */
> > > +             for (owner = mtx_owner(m); owner && TD_IS_RUNNING(owner); 
owner =
> > mtx_owner(m))
> > > +                     cpu_spinwait();
> > > +             if (mtx_unowned(m))
> > > +                     continue;
> > > +#endif       /* SMP && !NO_ADAPTIVE_MUTEXES */
> > >               turnstile_lock(&m->mtx_object);
> > >               v = m->mtx_lock;
> > >
> > > @@ -425,7 +435,7 @@
> > >                * Check if the lock has been released while spinning for
> > >                * the turnstile chain lock.
> > >                */
> > > -             if (v == MTX_UNOWNED) {
> > > +             if (mtx_unowned(m)) {
> > >                       turnstile_release(&m->mtx_object);
> > >                       cpu_spinwait();
> > >                       continue;
> > > @@ -837,6 +847,8 @@
> > >       mtx_validate(m);
> > >  #endif
> > >
> > > +
> > > +
> > >       /* Determine lock class and lock flags. */
> > >       if (opts & MTX_SPIN)
> > >               class = &lock_class_mtx_spin;
> > >
> >
> > --
> > John Baldwin
> >
> 

-- 
John Baldwin