Dmitry Konstantinov created CASSANDRA-21429:
-----------------------------------------------
Summary: SEPExecutor#maybeExecuteImmediately not always run tasks
immediate even if there is worker capacity
Key: CASSANDRA-21429
URL: https://issues.apache.org/jira/browse/CASSANDRA-21429
Project: Apache Cassandra
Issue Type: Improvement
Components: Local/Other
Reporter: Dmitry Konstantinov
Ad-hoc metrics:
{code:java}
INFO [SEPExecutor-maybeExecuteImmediately-stats] 2026-06-03T19:32:35,526
SEPExecutor.java:70 - SEPExecutor.maybeExecuteImmediately stats:
total=15000018, addTask=876687, ratio=0.05844572986512416 {code}
so, under read stress load we may get ~6% of scheduled tasks in a different
thread even if ReadStage pool size > Native-Transport pool size
{code:java}
public void maybeExecuteImmediately(Runnable task)
{
task = taskFactory.toExecute(task);
if (!takeWorkPermit(false))
{ addTask(task); // <== we can get into this branch even if we have
worker permits
}
else
{
try
{
task.run();
}
finally
{
returnWorkPermit();
// we have to maintain our invariant of always scheduling after any
work is performed
// in this case in particular we are not processing the rest of the
queue anyway, and so
// the work permit may go wasted if we don't immediately attempt to
spawn another worker
maybeSchedule();
}
}
} {code}
{code}
boolean takeWorkPermit(boolean takeTaskPermit)
{
int taskDelta = takeTaskPermit ? 1 : 0;
while (true)
{
long current = permits.get();
int workPermits = workPermits(current);
int taskPermits = taskPermits(current);
if (workPermits <= 0 || taskPermits == 0) // <== if we do not have
in progress tasks we return false here
return false;
if (permits.compareAndSet(current, combine(taskPermits - taskDelta,
workPermits - 1)))
{
return true;
}
}
}
{code}
--
This message was sent by Atlassian Jira
(v8.20.10#820010)
---------------------------------------------------------------------
To unsubscribe, e-mail: [email protected]
For additional commands, e-mail: [email protected]
