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Posted to dev@qpid.apache.org by "ASF GitHub Bot (JIRA)" <ji...@apache.org> on 2019/07/17 14:58:00 UTC
[jira] [Commented] (DISPATCH-1342) Replaced mutex with spin lock on
qd_message content
[ https://issues.apache.org/jira/browse/DISPATCH-1342?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16887132#comment-16887132 ]
ASF GitHub Bot commented on DISPATCH-1342:
------------------------------------------
franz1981 commented on issue #508: DISPATCH-1342 Replaced mutex with spin lock on qd_message content
URL: https://github.com/apache/qpid-dispatch/pull/508#issuecomment-505461704
@astitcher
I believe that the doc of spin lock is excessively conservative TBH (with good reasons, given how many archs it has to cover), but it gives nice hints to make things more resilient on not properly configured box/limited machines.
Although not written on the stone, the router need at least 2 HW threads to run properly (1 core + 1 I/O worker) and it's true that a single core machine with HyperThread will suffer by using spin locks. Same thing can be said if you run the router configuring (much) more threads then real cores...
In those cases I'm not quite sure the router will perform optimally, but makes sense to account for them too: in all the other cases, assuming the previous correctness conditions to be met, I believe using spin locks would be just a win resource-wise, given the peculiar design of the router (no thread pools, just fixed numbers of threads with specific roles).
I suggest, if not possible to accept this PR, to consider pooling mutexes to reduce the allocation/deallocation rate for such heavyweight kernel resources.
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> Replaced mutex with spin lock on qd_message content
> ---------------------------------------------------
>
> Key: DISPATCH-1342
> URL: https://issues.apache.org/jira/browse/DISPATCH-1342
> Project: Qpid Dispatch
> Issue Type: Improvement
> Components: Routing Engine
> Affects Versions: 1.7.0
> Reporter: Francesco Nigro
> Priority: Minor
>
> Given that qd_message creation and qd_message_free involves sys_mutex allocation/free and they are OS resources too, using spin locks will reduce the CPU/memory usage while performing such frequent operations.
> In addition it would make the router more reactive and resilient to OS thread scheduling while message->content is being concurrently accessed too, given that such accesses are meant to not last long and there is no need to involve OS arbitration to park/awake threads,
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