Messages in this thread | | | Date | Fri, 21 Dec 2012 22:07:56 -0500 | From | Steven Rostedt <> | Subject | Re: [RFC PATCH 2/3] x86,smp: proportional backoff for ticket spinlocks |
| |
On Fri, Dec 21, 2012 at 06:51:15PM -0500, Rik van Riel wrote: > Subject: x86,smp: proportional backoff for ticket spinlocks > > Simple fixed value proportional backoff for ticket spinlocks. > By pounding on the cacheline with the spin lock less often, > bus traffic is reduced. In cases of a data structure with > embedded spinlock, the lock holder has a better chance of > making progress. > > Signed-off-by: Rik van Riel <riel@redhat.com> > --- > arch/x86/kernel/smp.c | 6 ++++-- > 1 files changed, 4 insertions(+), 2 deletions(-) > > diff --git a/arch/x86/kernel/smp.c b/arch/x86/kernel/smp.c > index 20da354..4e44840 100644 > --- a/arch/x86/kernel/smp.c > +++ b/arch/x86/kernel/smp.c > @@ -118,9 +118,11 @@ static bool smp_no_nmi_ipi = false; > void ticket_spin_lock_wait(arch_spinlock_t *lock, struct __raw_tickets inc) > { > for (;;) { > - cpu_relax(); > - inc.head = ACCESS_ONCE(lock->tickets.head); > + int loops = 50 * (__ticket_t)(inc.tail - inc.head); > + while (loops--) > + cpu_relax();
-ENOCOMMENT
Please add a comment above to explain what it's doing. Don't expect people to check change logs. Also, explain why you picked 50.
-- Steve
> > + inc.head = ACCESS_ONCE(lock->tickets.head); > if (inc.head == inc.tail) > break; > } > > -- > To unsubscribe from this list: send the line "unsubscribe linux-kernel" in > the body of a message to majordomo@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html > Please read the FAQ at http://www.tux.org/lkml/
| |