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Posted to commits@cassandra.apache.org by be...@apache.org on 2014/07/15 19:21:30 UTC
[1/3] git commit: ninja fix comments in SharedExecutorPool
Repository: cassandra
Updated Branches:
refs/heads/trunk 8a5a82b8a -> 1c4768a88
ninja fix comments in SharedExecutorPool
Project: http://git-wip-us.apache.org/repos/asf/cassandra/repo
Commit: http://git-wip-us.apache.org/repos/asf/cassandra/commit/ca431888
Tree: http://git-wip-us.apache.org/repos/asf/cassandra/tree/ca431888
Diff: http://git-wip-us.apache.org/repos/asf/cassandra/diff/ca431888
Branch: refs/heads/trunk
Commit: ca431888efd91bb8a7900c0219bd821744153686
Parents: 0401761
Author: Benedict Elliott Smith <be...@apache.org>
Authored: Tue Jul 15 18:20:48 2014 +0100
Committer: Benedict Elliott Smith <be...@apache.org>
Committed: Tue Jul 15 18:20:48 2014 +0100
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.../cassandra/concurrent/SharedExecutorPool.java | 19 ++++++++++++-------
1 file changed, 12 insertions(+), 7 deletions(-)
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http://git-wip-us.apache.org/repos/asf/cassandra/blob/ca431888/src/java/org/apache/cassandra/concurrent/SharedExecutorPool.java
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diff --git a/src/java/org/apache/cassandra/concurrent/SharedExecutorPool.java b/src/java/org/apache/cassandra/concurrent/SharedExecutorPool.java
index e03ec57..161b326 100644
--- a/src/java/org/apache/cassandra/concurrent/SharedExecutorPool.java
+++ b/src/java/org/apache/cassandra/concurrent/SharedExecutorPool.java
@@ -35,17 +35,22 @@ import static org.apache.cassandra.concurrent.SEPWorker.Work;
* To keep producers from incurring unnecessary delays, once an executor is "spun up" (i.e. is processing tasks at a steady
* rate), adding tasks to the executor often involves only placing the task on the work queue and updating the
* task permits (which imposes our max queue length constraints). Only when it cannot be guaranteed the task will be serviced
- * promptly does the producer have to signal a thread itself to perform the work.
+ * promptly, and the maximum concurrency has not been reached, does the producer have to schedule a thread itself to perform
+ * the work ('promptly' in this context means we already have a worker spinning for work, as described next).
*
- * We do this by scheduling only if
- *
- * The worker threads schedule themselves as far as possible: when they are assigned a task, they will attempt to spawn
+ * Otherwise the worker threads schedule themselves: when they are assigned a task, they will attempt to spawn
* a partner worker to service any other work outstanding on the queue (if any); once they have finished the task they
* will either take another (if any remaining) and repeat this, or they will attempt to assign themselves to another executor
* that does have tasks remaining. If both fail, it will enter a non-busy-spinning phase, where it will sleep for a short
* random interval (based upon the number of threads in this mode, so that the total amount of non-sleeping time remains
- * approximately fixed regardless of the number of spinning threads), and upon waking up will again try to assign themselves
- * an executor with outstanding tasks to perform.
+ * approximately fixed regardless of the number of spinning threads), and upon waking will again try to assign itself to
+ * an executor with outstanding tasks to perform. As a result of always scheduling a partner before committing to performing
+ * any work, with a steady state of task arrival we should generally have either one spinning worker ready to promptly respond
+ * to incoming work, or all possible workers actively committed to tasks.
+ *
+ * In order to prevent this executor pool acting like a noisy neighbour to other processes on the system, workers also deschedule
+ * themselves when it is detected that there are too many for the current rate of operation arrival. This is decided as a function
+ * of the total time spent spinning by all workers in an interval; as more workers spin, workers are descheduled more rapidly.
*/
public class SharedExecutorPool
{
@@ -96,4 +101,4 @@ public class SharedExecutorPool
if (current == 0 && spinningCount.compareAndSet(0, 1))
schedule(Work.SPINNING);
}
-}
\ No newline at end of file
+}
[2/3] git commit: Merge branch 'cassandra-2.1.0' into cassandra-2.1
Posted by be...@apache.org.
Merge branch 'cassandra-2.1.0' into cassandra-2.1
Project: http://git-wip-us.apache.org/repos/asf/cassandra/repo
Commit: http://git-wip-us.apache.org/repos/asf/cassandra/commit/e66896b1
Tree: http://git-wip-us.apache.org/repos/asf/cassandra/tree/e66896b1
Diff: http://git-wip-us.apache.org/repos/asf/cassandra/diff/e66896b1
Branch: refs/heads/trunk
Commit: e66896b1d326c49ee8b7b20ef343490370ba968f
Parents: 8a2d8a1 ca43188
Author: Benedict Elliott Smith <be...@apache.org>
Authored: Tue Jul 15 18:21:01 2014 +0100
Committer: Benedict Elliott Smith <be...@apache.org>
Committed: Tue Jul 15 18:21:01 2014 +0100
----------------------------------------------------------------------
.../cassandra/concurrent/SharedExecutorPool.java | 19 ++++++++++++-------
1 file changed, 12 insertions(+), 7 deletions(-)
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[3/3] git commit: Merge branch 'cassandra-2.1' into trunk
Posted by be...@apache.org.
Merge branch 'cassandra-2.1' into trunk
Project: http://git-wip-us.apache.org/repos/asf/cassandra/repo
Commit: http://git-wip-us.apache.org/repos/asf/cassandra/commit/1c4768a8
Tree: http://git-wip-us.apache.org/repos/asf/cassandra/tree/1c4768a8
Diff: http://git-wip-us.apache.org/repos/asf/cassandra/diff/1c4768a8
Branch: refs/heads/trunk
Commit: 1c4768a8889122b40f57be10f8af8e2522a09ec8
Parents: 8a5a82b e66896b
Author: Benedict Elliott Smith <be...@apache.org>
Authored: Tue Jul 15 18:21:10 2014 +0100
Committer: Benedict Elliott Smith <be...@apache.org>
Committed: Tue Jul 15 18:21:10 2014 +0100
----------------------------------------------------------------------
.../cassandra/concurrent/SharedExecutorPool.java | 19 ++++++++++++-------
1 file changed, 12 insertions(+), 7 deletions(-)
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http://git-wip-us.apache.org/repos/asf/cassandra/blob/1c4768a8/src/java/org/apache/cassandra/concurrent/SharedExecutorPool.java
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