Oleg Kibirev created CASSANDRA-4681:
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Summary: SlabAllocator spends a lot of time in Thread.yield
Key: CASSANDRA-4681
URL: https://issues.apache.org/jira/browse/CASSANDRA-4681
Project: Cassandra
Issue Type: Bug
Components: Core
Affects Versions: 1.1.5
Environment: OEL Linux
Reporter: Oleg Kibirev
When profiling high volume inserts into Cassandra running on a host with fast
SSD and CPU, Thread.yield() invoked by SlabAllocator appeared as the top item
in CPU samples. The fix is to return a regular byte buffer if current slab is
being initialized by another thread. So instead of:
if (oldOffset == UNINITIALIZED)
{
// The region doesn't have its data allocated yet.
// Since we found this in currentRegion, we know that
whoever
// CAS-ed it there is allocating it right now. So spin-loop
// shouldn't spin long!
Thread.yield();
continue;
}
do:
if (oldOffset == UNINITIALIZED)
return ByteBuffer.allocate(size);
I achieved 4x speed up in my (admittedly specialized) benchmark.
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