4 Replies Latest reply on Mar 25, 2011 1:32 AM by Jeff Nadler

    BoundedConcurrentHashMap Eviction Performance

    Jeff Nadler Newbie

      After a few profilig sessions, I'm seeing lots of time in BoundedConcurentHashMap during eviction (DefaultDataContainer.purgeExpired).   This may be normal, I don't have anything to compare to.   I am using LRU eviction algorithm.  Please see the hotspots from my profiling session below.


      Has anyone else seen this while profiling an Infinispan app?   Is there anything I can do to improve performance here, or am I already as optimized as I'm going to get?


      Big thanks to anyone who can shed some light-







      63 seconds - org.infinispan.util.concurrent.BoundedConcurrentHashMap$HashIterator.advance

      38 seconds - org.infinispan.util.concurrent.BoundedConcurrentHashMap$HashIterator.hasNext

      40 seconds - org.infinispan.container.entries.ImmortalCacheEntry.isExpired

        • 1. BoundedConcurrentHashMap Eviction Performance
          Dan Berindei Expert

          If you look at the ImmortalCacheEntry implementation, isExpired() just returns false, so it shouldn't appear in the profiler output at all.


          You should make sure you're using sampling when profiling, otherwise small methods that are called often will appear to have disproportionately high CPU time.


          If you are using sampling, could you share your tests?

          • 2. BoundedConcurrentHashMap Eviction Performance
            Jeff Nadler Newbie

            D'oh.  Of course you're right Dan:  Thought I was using sampling but I was not.  


            Using sampling the eviction appears to be taking somewhat less time:


                 32s org.infinispan.container.DefaultDataContainer.purgeExpired


            If I drill down inside 'purgeExpired' it shows BoundedConcurrentHashMap$HashIterator.<init> but the sampling indicates only 25ms total spent here out of 32s total in purgeExpired; I assume this is a limitation of the sampling method.


            I believe that if I run eviction somewhat less frequently I will be able to find an acceptable tradeoff.

            • 3. BoundedConcurrentHashMap Eviction Performance
              Dan Berindei Expert

              If you're not instrumenting each method call it can be inlined and it won't show in the profiler, so it makes sense that you don't see anything under purgeExpired.


              That still seems like a lot of time in purgeExpired... How big is your cache? Do you use the default wakeupInterval or have you set it lower? And how long does your test take?

              • 4. BoundedConcurrentHashMap Eviction Performance
                Jeff Nadler Newbie

                Our wakeupInterval was set to 10 seconds at the time I ran this test.  Test ran for 20 minutes so perhaps 120 total invocations across each of 8 cache regions.  Eviction was approx 5% of the total CPU time during this test.  Less than 100k total cache entries. 


                I expect to be profiling again next week.   I have decreased wakeupInterval to 30 seconds so the impact should be less.