MySQL Bugs: #69392: Wasted work in waitForThreads()

Bug #69392	Wasted work in waitForThreads()
Submitted:	4 Jun 2013 0:05	Modified:	10 Jun 2013 14:10
Reporter:	Po-Chun Chang (OCA)	Email Updates:
Status:	Closed	Impact on me:	None
Category:	MySQL Server: Tests	Severity:	S5 (Performance)
Version:	5.6, 5.7	OS:	Any
Assigned to:	Magnus Blåudd	CPU Architecture:	Any
Tags:	patch, performance

Description:
The problem appears in version 5.6 and in the revision 5216 in
version 5.7.  I attached a simple one-line patch (patch.diff) that
fixes it.  This problem is similar to the already verified MySQL
#69207.

In method "waitForThreads()" in flexHammer.cpp, the loop on line 163 should 
break immediately after "cont" is set to 1. All the iterations after 
"cont" is set to 1 do not perform any useful work, at best they just
set "cont" again to 1.

There are two other similar problems at "flexBench.cpp" and "flexAsync.cpp",
in the functions with identical names (waitForThreads()).
I attached two more patches (patch2.diff, patch3.diff) for them.

How to repeat:
Once waitForThreads() is executed.

Suggested fix:
=== modified file 'storage/ndb/test/ndbapi/flexHammer.cpp'
--- storage/ndb/test/ndbapi/flexHammer.cpp	2013-02-26 05:45:28 +0000
+++ storage/ndb/test/ndbapi/flexHammer.cpp	2013-06-03 23:55:13 +0000
@@ -166,6 +166,7 @@
     for (int i = 0; i < tNoOfThreads ; i++) {
       if (threadArrayP[i].threadReady == 0) {
 	cont = 1;
+	break;
       } // if
     } // for
   } // while

Suggested patch for flexHammer.cpp

Attachment: patch.diff (text/plain), 376 bytes.

Suggested patch for flexBench.cpp

Attachment: patch2.diff (text/plain), 355 bytes.

Suggested patch for flexAsync.cpp

Attachment: patch3.diff (text/plain), 399 bytes.

Hello Po-Chun,

Thank you for the report and contribution.

Thanks,
Umesh

Thank you for your bug report. This issue has been committed to our source repository of that product and will be incorporated into the next release.

If necessary, you can access the source repository and build the latest available version, including the bug fix. More information about accessing the source trees is available at

    http://dev.mysql.com/doc/en/installing-source.html

Fixed from MySQL Cluster 7.0.39 and upwards

For documentation, see BUG#69393.