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Richard (Gaz) Gasiorowski
System z - Linux Product Manager
Portfolio Platform Services
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Leland Lucius <[email protected]>
Sent by: Linux on 390 Port <[email protected]>
04/30/2009 03:04 PM
Please respond to
Linux on 390 Port <[email protected]>


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Subject
Re: cpuplugd and hung connections/defunct processes?




Leland,

By the way How is it up there in the great white north?  This type of
condition you have experienced with a CLOSED_Wait is not uncommon in WAZ.
But again it is up to WAZ to close the connection once the WAIT is
detected.  Here are some scenarios where CLOSED_WAIT can occur
Local Server closes first:
ESTABLISHED -> FIN_WAIT_1-> FIN_WAIT_2 -> TIME_WAIT -> CLOSED.
Remote Server closes first:
ESTABLISHED -> CLOSE_WAIT -> LAST_ACK -> CLOSED.
Local and Remote Server close at the same time:
ESTABLISHED -> FIN_WAIT_1-> CLOSING ->TIME_WAIT -> CLOSED.

Some of TCP parms that can be of help
TCP_TIME_INTERVAL - Defaul value is 240000 milliseconds = 4 minutes.
Recommended is 60000 milliseconds
TCP_FIN_WAIT_2_FLUSH_INTERVAL - Default Value is 675000 milliseconds.
Recommended is 67500 milliseconds
TCP_KEEPALIVE_INTERVAL -Default Value is 7200000 milliseconds. Recommended
is 15000 milliseconds
Connection backlog - Default value is 128. Recommended is 8000

Richard Gasiorowski wrote:
> Leland,
>
> I don't see how cpuplugd would have anything to do with sockets waiting
to
> be closed by the application.
I was thinking that "maybe" there might have been some sort of race
condition or locking issues when the addition CPU was put offline.  Mind
you, I don't want this to be cpuplugd so if you don't think it could be
cpuplugd, then that's good enough for me.

> The SYN_RECV  is a result of the
> CLOSED_wait is what it seems to me.  This error in abundance normally is
> linked to the app. Websphere should notice the bad connection and issue
a
> close thru the OS.
> the obvious question is - was there maintenance applied to Websphere
> recently?
>
Well that would be a nice answer to have wouldn't it.  I don't think I'm
going to get a good answer on that one, but I may be able to sleuth it
out.

Leland

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