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https://issues.apache.org/jira/browse/HTTPCORE-155?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12657832#action_12657832
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Marc Beyerle commented on HTTPCORE-155:
---------------------------------------
Hi Oleg,
Thank you for your positive feedback. You are really tough to convince ;-)
Following your suggestions, I changed a few things in the code itself, without
changing the ideas behind the patch: The queue is a regular instance member
now, and I don't exhibit the queue itself to the "outside world", but rather
only offer an add()... method.
In addition, I now changed the existing code as little as possible - for
example, I moved the processing of the queue in an extra method, so that the
amount of lines of code in the main loop in AbstractIOReactor grows as little
as possible.
Here's a bit more explanation of what I implemented, just to give you an idea
about the decisions I had to take: Since the constructor of IOSessionImpl
already depends on SelectionKey and contains exception handling, it's not much
additional cost to add a reference to the calling AbstractIOReactor (plus
check) there.
The reason, why the loop in processPendingInterestOps() is entirely within the
synchronized block, is to process all pending operations, which exist at the
time of invocation, in one operation. If for example only the
interestOpsQueue.remove() call was placed within the synchronized block, then
this would allow the queue to grow while the processing is in progress.
The only detail that I can think of right now, which one could implement
differently, is to move the check for a valid operationType from
addInterestOpsQueueElement() to the constructor of IOSessionQueueElement. But
this would require exception handling there, which is more expensive than the
if/else check in the method. Anyways, the queue elements are checked in detail
in the add()... method, before they enter the queue.
I ran some tests with both JVMs again, and the above changes didn't have a
negative effect on throughput. Again, I couldn't observe any exceptions.
Cheers,
Marc
> Performance issues with IBM JRE 6.0
> -----------------------------------
>
> Key: HTTPCORE-155
> URL: https://issues.apache.org/jira/browse/HTTPCORE-155
> Project: HttpComponents HttpCore
> Issue Type: Bug
> Components: HttpCore NIO
> Affects Versions: 4.0-beta1
> Environment: Windows 2003 SP2 - IBM J2RE 1.6.0 build 2.4 - HTTPCore
> Beta1 - Dual Core CPU 3.0Ghz - 1Gbps networking
> Reporter: Tom McSorley
> Fix For: 4.1
>
> Attachments: AbstractIOReactor.diff, AbstractIOReactor.java,
> IOSessionImpl.diff, IOSessionImpl.java,
> javacore.20081203.153723.32300.0001.txt, patch.08-12-17.tar.gz
>
>
> I'm issuing a second HTTP Request on a connection that has very recently
> returned a null for the submitRequest() call... this 2nd request is being
> issued approximately 500ms after the submitRequest() null is returned... so
> the connection has just been established, an HTTP Request/Response-200 cycle
> has completed just prior to this 2nd request being issued. I'm seeing
> unusually long delays in the requestOutput() call (verified by surrounding
> timing prints)... that can range anywhere from a few milliseconds on up to 60
> seconds... It eventually unwinds, and then the submitRequest() is called...
> this 2nd request is dispatched and works fine... but, it is delayed
> considerably... Is this a known issue and is there a possible work-around?
> Here's the JVM related thread information:
> The thread being delayed and stuck in the requestOutput() call for a long
> time (mostly longer than 5 seconds):
> 3XMTHREADINFO "pool-2-thread-5" TID:0x2AEECE00, j9thread_t:0x2A7189A8,
> state:B, prio=5
> 3XMTHREADINFO1 (native thread ID:0x1B44, native priority:0x5,
> native policy:UNKNOWN)
> 4XESTACKTRACE at
> sun/nio/ch/SelectionKeyImpl.interestOps(SelectionKeyImpl.java:60)
> 4XESTACKTRACE at
> org/apache/http/impl/nio/reactor/IOSessionImpl.setEvent(IOSessionImpl.java:113)
> 4XESTACKTRACE at
> org/apache/http/impl/nio/NHttpConnectionBase.requestOutput(NHttpConnectionBase.java:158)
> .... (non important stack information removed)
> 4XESTACKTRACE at
> java/util/concurrent/ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:919)
> 4XESTACKTRACE at java/lang/Thread.run(Thread.java:735)
> Here's the monitor that this thread is blocked and waiting on:
> 2LKMONINUSE sys_mon_t:0x2A708AF8 infl_mon_t: 0x2A708B30:
> 3LKMONOBJECT sun/nio/ch/uti...@00b09208/00B09214: Flat locked by "I/O
> dispatcher 7" (0x2A208E00), entry count 1
> 3LKWAITERQ Waiting to enter:
> 3LKWAITER "pool-2-thread-5" (0x2AEECE00)
> And here's the thread that currently has this monitor locked:
> 3XMTHREADINFO "I/O dispatcher 7" TID:0x2A208E00, j9thread_t:0x2A6EC73C,
> state:R, prio=5
> 3XMTHREADINFO1 (native thread ID:0x830, native priority:0x5,
> native policy:UNKNOWN)
> 4XESTACKTRACE at
> sun/nio/ch/WindowsSelectorImpl$SubSelector.poll0(Native Method)
> 4XESTACKTRACE at
> sun/nio/ch/WindowsSelectorImpl$SubSelector.poll(WindowsSelectorImpl.java:308(Compiled
> Code))
> 4XESTACKTRACE at
> sun/nio/ch/WindowsSelectorImpl$SubSelector.access$500(WindowsSelectorImpl.java(Compiled
> Code))
> 4XESTACKTRACE at
> sun/nio/ch/WindowsSelectorImpl.doSelect(WindowsSelectorImpl.java:162(Compiled
> Code))
> 4XESTACKTRACE at
> sun/nio/ch/SelectorImpl.lockAndDoSelect(SelectorImpl.java:69(Compiled Code))
> 4XESTACKTRACE at
> sun/nio/ch/SelectorImpl.select(SelectorImpl.java:80(Compiled Code))
> 4XESTACKTRACE at
> org/apache/http/impl/nio/reactor/AbstractIOReactor.execute(AbstractIOReactor.java:121)
> 4XESTACKTRACE at
> org/apache/http/impl/nio/reactor/BaseIOReactor.execute(BaseIOReactor.java:70)
> 4XESTACKTRACE at
> org/apache/http/impl/nio/reactor/AbstractMultiworkerIOReactor$Worker.run(AbstractMultiworkerIOReactor.java:318)
> 4XESTACKTRACE at java/lang/Thread.run(Thread.java:735)
> I should also note that we're attempting to use 1000 client instances on this
> single system... each with potentially 2 active connections simultaneously...
> there is also virtually no CPU load (i.e. less then 5%) on this system...
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