On Mon, Dec 30, 2013 at 2:44 PM, Ben Pfaff <b...@nicira.com> wrote:
> On Mon, Dec 30, 2013 at 02:37:38PM -0800, Pravin Shelar wrote:
>> On Mon, Dec 30, 2013 at 1:34 PM, Ben Pfaff <b...@nicira.com> wrote:
>> > On Mon, Dec 30, 2013 at 11:10:22AM -0800, Pravin Shelar wrote:
>> >> On Mon, Dec 30, 2013 at 10:49 AM, Ben Pfaff <b...@nicira.com> wrote:
>> >> > On Mon, Dec 30, 2013 at 10:40:13AM -0800, Pravin Shelar wrote:
>> >> >> On Fri, Dec 27, 2013 at 8:03 PM, Ben Pfaff <b...@nicira.com> wrote:
>> >> >> > ovsthread_counter is an abstract interface that could be implemented
>> >> >> > different ways. The initial implementation is simple but less than
>> >> >> > optimally efficient.
>> >> >> >
>> >> >> > Signed-off-by: Ben Pfaff <b...@nicira.com>
>> >> >> > +void
>> >> >> > +ovsthread_counter_inc(struct ovsthread_counter *c, unsigned long
>> >> >> > long int n)
>> >> >> > +{
>> >> >> > + c = &c[hash_int(ovsthread_id_self(), 0) % N_COUNTERS];
>> >> >> > +
>> >> >> Does it make sense optimize this locking so that threads running on
>> >> >> same numa-node likely share lock?
>> >> >> we can use process id hashing to achieve it easily.
>> >> >
>> >> > Yes, that makes a lot of sense. How do we do it?
>> >> >
>> >> Use processor id (sched_getcpu()) to hash it. In case of
>> >> sched_getcpu() is not available then we can read thread affinity using
>> >> sched_getaffinity() and return assigned CPU, in properly optimized
>> >> environment we can assume that a thread wold be pinned to one cpu
>> >> only. But I am not sure of doing on platforms other than linux.
>> >
>> > That's reasonable.
>> >
>> > But, on second thought, I am not sure of the benefit from threads on
>> > the same node sharing a lock. I see that there are benefits from
>> > threads on different nodes having different locks, but I'm not sure
>> > that using only one lock on a single node really saves anything. What
>> > do you think?
>>
>> Then how about having per-cpu lock?
>
> That would be ideal but how would I do it?
Create array of ovsthread_counter__ for all possible cpu. So
N_COUNTERS would be variable equal to num of possible cpu. To
increment use counter at index sched_getcpu().
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