33% of compaction time spent in StreamingHistogram.update()

CREATE TABLE biggraphite.datapoints_11520p_60s (
    metric uuid,
    time_start_ms bigint,
    offset smallint,
    count int,
    value double,
    PRIMARY KEY ((metric, time_start_ms), offset)
) WITH CLUSTERING ORDER BY (offset DESC);
AND compaction = {'class': 'org.apache.cassandra.db.compaction.TimeWindowCompactionStrategy', 'compaction_window_size': '6', 'compaction_window_unit': 'HOURS', 'max_threshold': '32', 'min_threshold': '6'}

Keyspace : biggraphite
        Read Count: 1822
        Read Latency: 1.8870054884742042 ms.
        Write Count: 2212271647
        Write Latency: 0.027705127678653473 ms.
        Pending Flushes: 0
                Table: datapoints_11520p_60s
                SSTable count: 47
                Space used (live): 300417555945
                Space used (total): 303147395017
                Space used by snapshots (total): 0
                Off heap memory used (total): 207453042
                SSTable Compression Ratio: 0.4955200053039823
                Number of keys (estimate): 16343723
                Memtable cell count: 220576
                Memtable data size: 17115128
                Memtable off heap memory used: 0
                Memtable switch count: 2872
                Local read count: 0
                Local read latency: NaN ms
                Local write count: 1103167888
                Local write latency: 0.025 ms
                Pending flushes: 0
                Percent repaired: 0.0
                Bloom filter false positives: 0
                Bloom filter false ratio: 0.00000
                Bloom filter space used: 105118296
                Bloom filter off heap memory used: 106547192
                Index summary off heap memory used: 27730962
                Compression metadata off heap memory used: 73174888
                Compacted partition minimum bytes: 61
                Compacted partition maximum bytes: 51012
                Compacted partition mean bytes: 7899
                Average live cells per slice (last five minutes): NaN
                Maximum live cells per slice (last five minutes): 0
                Average tombstones per slice (last five minutes): NaN
                Maximum tombstones per slice (last five minutes): 0
                Dropped Mutations: 0