Hi, We’re seeing some weird behavior from the hdfs daemon on google cloud environment when we use accumulo Scanner to sequentially scan a table. Top reports 200-300% cpu usage for the hdfs daemon. Accumulo is also around 500%. iostat %util is low. avgrq-sz is low, rMB/s is low, there’s lots of free memory. It seems like something causes the hdfs daemon to consume a lot of cpu and not to send enough read requests to the disk (ssd actually, so disk is super fast and vastly under-utilized). The process which sends scan requests to accumulo is 500% active (using 3 query batch threads and aggressive scan-batch-size/read-ahead-threashold values). So it seems like somehow hdfs is the bottleneck. On another cluster we rarely see hdfs daemon going over 10% cpu usage. Any idea what the issue could be?
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