Messages in this thread |  | | Date | Thu, 10 Jan 2013 05:15:15 -0800 | Subject | Re: [PATCH 4/5] x86,smp: keep spinlock delay values per hashed spinlock address | From | Michel Lespinasse <> |
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On Thu, Jan 10, 2013 at 5:05 AM, Rik van Riel <riel@redhat.com> wrote: > Eric, > > with just patches 1-3, can you still reproduce the > regression on your system? > > In other words, could we get away with dropping the > complexity of patch 4, or do we still need it?
To be clear, I must say that I'm not opposing patch 4 per se. I think we should not rely on it to avoid regressions, as patch 3 needs to be robust enough to do that on its own. However, it may very well be that having different constants for each lock (or for each hash bucket as a proxy) helps - if lock B has a consistently longer hold time than lock A, having them in separate hash buckets will allow us to use optimal tunings for both, but if they collide or if we don't have a hash table, we'll use a delay that is close to A's value for both, which is safe (shouldn't introduce regressions) but not optimal.
In other words, I really don't want us to depend on the hash table for robustness but I think it's fine to have it for extra performance (as it's actually very short)
-- Michel "Walken" Lespinasse A program is never fully debugged until the last user dies.
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