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  1. Couchbase Server
  2. MB-42092

Remove hash detail stats from cbcollect

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    • Story Points:
      1

      Description

      During qualification testing of 6.6.0 it was noted that memcached stats hash detail has a sizeable impact on server performance (ops/s).

      The exact cause of that slowdown has not been confirmed, but the belief is that given "hash" must traverse every item in each vBucket's HashTable and (while under lock) accumulate various stats including histograms of chain depth :-

      class HashTableDepthStatVisitor : public HashTableDepthVisitor {
      public:
          void visit(int bucket, int depth, size_t mem) {
              (void)bucket;
              // -1 is a special case for min.  If there's a value other than
              // -1, we prefer that.
              min = std::min(min == -1 ? depth : min, depth);
              max = std::max(max, depth);
              depthHisto.add(depth);
              size += depth;
              memUsed += mem;
          }
      

      While this is being investigated and improved, temporarily remove this stat call from cbcollect to avoid impacting normal operation in customer environments.

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          Activity

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          build-team Couchbase Build Team added a comment -

          Build couchbase-server-6.6.1-9144 contains ns_server commit a28eb8f with commit message:
          MB-42092: Remove hash details stats from cbcollect_info

          Show
          build-team Couchbase Build Team added a comment - Build couchbase-server-6.6.1-9144 contains ns_server commit a28eb8f with commit message: MB-42092 : Remove hash details stats from cbcollect_info
          Hide
          build-team Couchbase Build Team added a comment -

          Build couchbase-server-7.0.0-3536 contains ns_server commit a28eb8f with commit message:
          MB-42092: Remove hash details stats from cbcollect_info

          Show
          build-team Couchbase Build Team added a comment - Build couchbase-server-7.0.0-3536 contains ns_server commit a28eb8f with commit message: MB-42092 : Remove hash details stats from cbcollect_info
          Hide
          steve.watanabe Steve Watanabe added a comment -

          Wayne Siu I'm fairly sure all the changes tracked by this ticket are in but will wait for James/Daniel to resolve the ticket.

          Show
          steve.watanabe Steve Watanabe added a comment - Wayne Siu I'm fairly sure all the changes tracked by this ticket are in but will wait for James/Daniel to resolve the ticket.
          Hide
          owend Daniel Owen added a comment -

          Hi all, Apologies. All changes are in. I will mark as resolved.

          Show
          owend Daniel Owen added a comment - Hi all, Apologies. All changes are in. I will mark as resolved.

            People

            Assignee:
            owend Daniel Owen
            Reporter:
            james.harrison James Harrison
            Votes:
            0 Vote for this issue
            Watchers:
            6 Start watching this issue

              Dates

              Created:
              Updated:
              Resolved:

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