Hi, I'm investigating LWT performance with C* 3.11.3. It looks that the performance is bounded by messaging latency when many requests are issued concurrently.
According to the source code, the number of messaging threads per node is only 1 thread for incoming and 1 thread for outbound "small" message to another node. I guess these threads are frequently interrupted because many threads are executed when many requests are issued. Especially, I think it affects the LWT performance when many LWT requests which need lots of inter-node messaging are issued. I measured that latency. It took 2.5 ms in average to enqueue a message at a node and to receive the message at the **same** node with 96 concurrent LWT writes. Is it normal? I think it is too big latency, though a message was sent to the same node. Decreasing numbers of other threads like `concurrent_counter_writes`, `concurrent_materialized_view_writes` reduced a bit the latency. Can I change any other parameter to reduce the latency? I've tried using message coalescing, but they didn't reduce that. * Environment - 3 node cluster - Replication factor: 3 - Node instance: AWS EC2 i3.xlarge * C* configuration - Apache Cassandra 3.11.3 - commitlog_sync: batch - concurrent_reads: 32 (default) - concurrent_writes: 32 (default) Thanks, Yuji
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