graham sanderson created CASSANDRA-7546:
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Summary: AtomicSortedColumns.addAllWithSizeDelta has a spin lock
that allocates memory
Key: CASSANDRA-7546
URL: https://issues.apache.org/jira/browse/CASSANDRA-7546
Project: Cassandra
Issue Type: Bug
Reporter: graham sanderson
In order to preserve atomicity, this code attempts to read, clone/update, then
CAS the state of the partition.
Under heavy contention for updating a single partition this can cause some
fairly staggering memory growth (the more cores on your machine the worst it
gets).
Whilst many usage patterns don't do highly concurrent updates to the same
partition, hinting today, does, and in this case wild (order(s) of magnitude
more than expected) memory allocation rates can be seen (especially when the
updates being hinted are small updates to different partitions which can happen
very fast on their own) - see CASSANDRA-7545
It would be best to eliminate/reduce/limit the spinning memory allocation
whilst not slowing down the very common un-contended case.
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