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Bug 347412

Summary:

[dstore] Need an option to set TCP NODELAYACKS

Product:

[Tools] Target Management

Reporter:

Missing name <olivier.gauneau>

Component:

RSE

Assignee:

David McKnight <dmcknigh>

Status:

RESOLVED FIXED

QA Contact:

Martin Oberhuber <mober.at+eclipse>

Severity:

major

Priority:

CC:

xuanchen

Version:

3.2.1

Flags:

xuanchen: review+

Target Milestone:

3.3 RC3

Hardware:

Other

OS:

other

Whiteboard:

Bug Depends on:

Bug Blocks:

347445

Attachments:

Description	Flags
patch to provide TCPNODELAY option	none
patch fixing the build on J2SE-1.4	none
patch with option described in constants file	none

Description Missing name

2011-05-27 04:51:06 EDT

Analysis of TCP traffic might show packets delayed of 200ms on the receiving side for some commands. This is caused by delay ack.

When the DELAYACKS is active, the ACK for a particular inbound packet with data will be delayed 200ms seconds if the inbound packet has a payload of less than the MSS.  Looking at the sniffer trace, the payload at the time when you see the 200ms is about 300 bytes (smaller than the MSS), which supports the theory that the DELAYACKS is active.

To turn off the delay ack on the MVS side, you can code NODELAYACKS on the TCPCONFIG statement (global) or you can code it on the PORT reservation statement for the particular port being used. 

However it will be useful to be able to set it on the socket in RSE as well using _socket.setTcpNoDelay(true);

Comment 1 Missing name

2011-05-27 04:52:55 EDT

A test with NODELAY shows great improvement on performance

Comment 2 Martin Oberhuber

2011-05-27 06:23:44 EDT

Is this request specific to dstore?
Does it affect the client only, or server only, or both?

Comment 3 Missing name

2011-05-27 06:39:05 EDT

Problem is on both sides client and server and I assume it is specific to dstore.
I have worked on this issue with David McKnight who will add more information.

Comment 4 David McKnight

2011-05-27 08:20:49 EDT

Created attachment 196749 [details]
patch to provide TCPNODELAY option

Comment 5 David McKnight

2011-05-27 08:21:22 EDT

Xuan, could you please review this?

Comment 6 Xuan Chen

2011-05-27 13:51:21 EDT

The fix looks good.  Thanks.

Comment 7 David McKnight

2011-05-27 13:55:28 EDT

Thanks for the review, Xuan.  I've committed the change to cvs.

Comment 8 Martin Oberhuber

2011-05-30 04:40:13 EDT

Created attachment 196872 [details]
patch fixing the build on J2SE-1.4

This checkin broke the build, because dstore.core must still be J2SE-1.4 compliant and Boolean.parseBoolean() is not in J2SE-1.4

I fixed the issue by converting to
   Boolean.valueOf(s).booleanValue().

Please also apply this fix to the 3.2.2+ Stream, which is currently also broken.
And, please ensure that a J2SE-1.4 JVM is registered in your Workspace (Preferences : Java : JVM's) in order to detect such issues in your workspace.

Comment 9 Martin Oberhuber

2011-05-30 04:47:21 EDT

I released the change for 3.3RC3.

Shouldn't we document system properties like the new DSTORE_TCP_NO_DELAY somewhere ?

Comment 10 David McKnight

2011-05-30 08:21:57 EDT

Created attachment 196888 [details]
patch with option described in constants file

Other properties like this have been defined in a constants file and described there as this patch does.

Comment 11 Martin Oberhuber

2011-05-31 08:50:58 EDT

I released the update for 3.3rc3, but cannot build currently due to bug 347744 .