users@grizzly.java.net

Re: do select spin on linux

From: John Franey <jjfraney_at_gmail.com>
Date: Wed, 15 Apr 2009 16:26:58 -0400

On Tue, Apr 14, 2009 at 9:11 PM, Jeanfrancois Arcand <
Jeanfrancois.Arcand_at_sun.com> wrote:

> Salut,
>
> John Franey wrote:
>
>> Jeanfrancois,
>>
>> I'm embarrassed to say, I have found a bug in my test case code. At this
>> point, I do not have a test case for this behavior.
>>
>> My apologies.
>>
>
> No problem. What was the issue with the test? I'm still interested to
> reproduce the issue as I suspect a JDK bug.
>

 I forgot that select will return zero keys when selector.wakeup is called,
and I assumed I had caught the problem. My confusion.



>
> Thanks!
>
> -- Jeanfrancois
>
>
>> John
>>
>>
>> On Tue, Apr 14, 2009 at 10:14 AM, Jeanfrancois Arcand <
>> Jeanfrancois.Arcand_at_sun.com <mailto:Jeanfrancois.Arcand_at_sun.com>> wrote:
>>
>> Salut,
>>
>> back online
>>
>>
>> John Franey wrote:
>>
>> Jeanfrancois,
>>
>> Just a couple of clarifications:
>>
>> 1) Running from the command line needs the jar files too. Sorry
>> I gave the impression that it was too easy. I think its easiest
>> to run from IDE, especially since a debugger is needed. I hope
>> that is ok.
>>
>>
>> OK I will try to reproduce the issue but I usually don't use IDE (I
>> use vim :-)).
>>
>>
>>
>>
>> 2) Also, the BReceiver won't be idle during the rest sleeps.
>> Sorry about that. Instead, once the exception occurs, simply
>> kill the UDPSender process, then you will be sure the BReceiver
>> is not receiving any new packets.
>>
>>
>> OK. BTW I've talked to the NIO/JDK lead and nothing about spinning
>> selector has been reported on jdk 4/5/6 so we might need to closely
>> look at your code.
>>
>> Thanks
>>
>> -- Jeanfrancois
>>
>>
>>
>> Regards,
>> John
>>
>>
>>
>> On Thu, Apr 9, 2009 at 2:31 PM, John Franey <jjfraney_at_gmail.com
>> <mailto:jjfraney_at_gmail.com> <mailto:jjfraney_at_gmail.com
>>
>> <mailto:jjfraney_at_gmail.com>>> wrote:
>>
>> Jeanfrancois,
>>
>> I got lucky, here is a test case. (gmail didn't let me send
>> it as
>> zip, so its a jar).
>>
>> this is a maven project, I guess you can build and run.
>>
>> There are two main classes.
>>
>> A receiver, BReceiver, and a sender, UDPSender.
>>
>> I run these from eclipse. I guess your IDE will let your run
>> them
>> easily, but I guess from the command line something easy like:
>> java -cp target/classes grizzlyproto/BReceiver would run.
>>
>> BReciever cycles a single udp port through many connections.
>> UDPSender sends datagrams to that port at high rate.
>>
>> Periodically, BReceiver pauses at a time when there should be
>> no cpu
>> charges to that process. Not sure this helps, but the
>> intention was
>> that if the process is using cpu at this time, then the
>> selector is
>> spinning.
>>
>> Within a few moment, BReceiver will get an exception (I do
>> not know
>> if the exception is related to the problem). Then you can set
>> breakpoint on Controller.doSelect's return from
>> selectorHandler.select (at line 329) to inspect value of
>> readyKeys. Its empty.
>>
>>
>> Here are my system specificaitons (from ubuntu 8.10)
>> Linux isidore 2.6.27-11-generic #1 SMP Thu Jan 29 19:28:32
>> UTC 2009
>> x86_64 GNU/Linux
>>
>>
>> I get the same behavior on both of these:
>>
>> java version "1.6.0_12"
>> Java(TM) SE Runtime Environment (build 1.6.0_12-b04)
>> Java HotSpot(TM) 64-Bit Server VM (build 11.2-b01, mixed mode)
>>
>> and
>>
>> java version "1.6.0_03"
>> Java(TM) SE Runtime Environment (build 1.6.0_03-b05)
>> BEA JRockit(R) (build
>> R27.5.0-110-94909-1.6.0_03-20080204-1558-linux-x86_64,
>> compiled mode)
>>
>>
>> Regards,
>> John
>>
>>
>>
>> On Thu, Apr 9, 2009 at 2:00 PM, John Franey
>> <jjfraney_at_gmail.com <mailto:jjfraney_at_gmail.com>
>> <mailto:jjfraney_at_gmail.com <mailto:jjfraney_at_gmail.com>>> wrote:
>>
>> Thanks.
>>
>>
>> On Thu, Apr 9, 2009 at 1:02 PM, Jeanfrancois Arcand
>> <Jeanfrancois.Arcand_at_sun.com
>> <mailto:Jeanfrancois.Arcand_at_sun.com>
>> <mailto:Jeanfrancois.Arcand_at_sun.com
>> <mailto:Jeanfrancois.Arcand_at_sun.com>>> wrote:
>>
>> Salut,
>>
>>
>> John Franey wrote:
>>
>> Hi,
>>
>> I'm running stress tests on linux. At some
>> point, cpu
>> utilization goes high. I've verified using the
>> debugger
>> that Controller.doSelect gets zero keys back from
>> handler's select.
>>
>>
>> Yes this is an issue I've reported awhile ago to the JDK
>> team. This sounds like bugparade 6403933
>>
>>
>> http://bugs.sun.com/bugdatabase/view_bug.do?bug_id=6403933
>>
>> A connection is reset causes the file descriptor to be
>> selected with events POLLHUP and POLLERR but unless
>> there is
>> data waiting to be read then channel will not be
>> selected.
>> It's a awkward problem.
>>
>> This has been fixed in JDK 7 build 50 and will be
>> included
>> in JDK 6u16.
>>
>>
>> The last statement in the evaluation of this bug nails
>> it, and
>> the load pattern described in this bug matches mine:
>> http://bugs.sun.com/view_bug.do?bug_id=6693490
>>
>> It sounds like the same root cause?
>>
>>
>>
>> Google search led me to this page at apache mina
>> jira
>> DIRMINA-678
>> <https://issues.apache.org/jira/browse/DIRMINA-678
>> >.
>>
>> Please see especially, this comment from Emannual
>> Lecharmy (31/Mar/09 03:23 PM)
>> <
>> https://issues.apache.org/jira/browse/DIRMINA-678?focusedCommentId=12696711&page=com.atlassian.jira.plugin.system.issuetabpanels%3Acomment-tabpanel#action_12696711
>> <
>> https://issues.apache.org/jira/browse/DIRMINA-678?focusedCommentId=12696711&page=com.atlassian.jira.plugin.system.issuetabpanels%3Acomment-tabpanel#action_12696711
>> >
>> <
>> https://issues.apache.org/jira/browse/DIRMINA-678?focusedCommentId=12696711&page=com.atlassian.jira.plugin.system.issuetabpanels%3Acomment-tabpanel#action_12696711
>> <
>> https://issues.apache.org/jira/browse/DIRMINA-678?focusedCommentId=12696711&page=com.atlassian.jira.plugin.system.issuetabpanels%3Acomment-tabpanel#action_12696711
>> >>>.
>>
>>
>> So, I'm looking for this 'beautiful hack' in the
>> Controller source code for 1.9.11 and am not
>> seeing it.
>> I think maybe I'm blind :) or the hack is in
>> grizzly
>> 2.0? If its in 2.0, do you think I can make it
>> fit into
>> 1.9.11? Or do you advise I try my application on
>> 2.0 trunk?
>>
>>
>> I didn't put the hack there (just for Comet) as I
>> never saw
>> it on the Controller. Can you share a test case?
>>
>>
>> I don't have a test case and am working on one. I would be
>> surprised if I can get it to happen without a lot of work.
>>
>> Is there a code sample from comet that has this hack in it
>> to
>> see if I can make the same change for my app?
>>
>> Thanks
>>
>> -- Jeanfrancois
>>
>>
>>
>> Thanks,
>> John
>>
>>
>>
>>
>>
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