Hi all,

I've been searching a lot and I'm struggling to get a resolve on how to interpret my IOZone report (with respect to Parent vs Child throughput):

Code:
Iozone: Performance Test of File I/O
	        Version $Revision: 3.242 $
		Compiled for 64 bit mode.
		Build: linux-AMD64 

	Contributors:William Norcott, Don Capps, Isom Crawford, Kirby Collins
	             Al Slater, Scott Rhine, Mike Wisner, Ken Goss
	             Steve Landherr, Brad Smith, Mark Kelly, Dr. Alain CYR,
	             Randy Dunlap, Mark Montague, Dan Million, 
	             Jean-Marc Zucconi, Jeff Blomberg,
	             Erik Habbinga, Kris Strecker, Walter Wong.

	Run began: Tue Dec 21 07:52:41 2010

	Record Size 4 KB
	File size set to 131072 KB
	Command line used: iozone -r 4k -s 128m -i 0 -i 1 -l 1 -u 4
	Output is in Kbytes/sec
	Time Resolution = 0.000001 seconds.
	Processor cache size set to 1024 Kbytes.
	Processor cache line size set to 32 bytes.
	File stride size set to 17 * record size.
	Min process = 1 
	Max process = 4 
	Throughput test with 1 process
	Each process writes a 131072 Kbyte file in 4 Kbyte records

	Children see throughput for  1 initial writers 	=  301113.50 KB/sec
	Parent sees throughput for  1 initial writers 	=    4523.09 KB/sec
	Min throughput per process 			=  301113.50 KB/sec 
	Max throughput per process 			=  301113.50 KB/sec
	Avg throughput per process 			=  301113.50 KB/sec
	Min xfer 					=  131072.00 KB

	Children see throughput for  1 rewriters 	=  581653.19 KB/sec
	Parent sees throughput for  1 rewriters 	=    1721.79 KB/sec
	Min throughput per process 			=  581653.19 KB/sec 
	Max throughput per process 			=  581653.19 KB/sec
	Avg throughput per process 			=  581653.19 KB/sec
	Min xfer 					=  131072.00 KB

	Children see throughput for  1 readers 		= 1179321.50 KB/sec
	Parent sees throughput for  1 readers 		=   38684.36 KB/sec
	Min throughput per process 			= 1179321.50 KB/sec 
	Max throughput per process 			= 1179321.50 KB/sec
	Avg throughput per process 			= 1179321.50 KB/sec
	Min xfer 					=  131072.00 KB

	Children see throughput for 1 re-readers 	= 1186332.62 KB/sec
	Parent sees throughput for 1 re-readers 	= 1181638.31 KB/sec
	Min throughput per process 			= 1186332.62 KB/sec 
	Max throughput per process 			= 1186332.62 KB/sec
	Avg throughput per process 			= 1186332.62 KB/sec
	Min xfer 					=  131072.00 KB


	Each process writes a 131072 Kbyte file in 4 Kbyte records

	Children see throughput for  2 initial writers 	=  412720.11 KB/sec
	Parent sees throughput for  2 initial writers 	=    2382.57 KB/sec
	Min throughput per process 			=  206328.03 KB/sec 
	Max throughput per process 			=  206392.08 KB/sec
	Avg throughput per process 			=  206360.05 KB/sec
	Min xfer 					=  130396.00 KB

	Children see throughput for  2 rewriters 	=  945912.50 KB/sec
	Parent sees throughput for  2 rewriters 	=    2320.70 KB/sec
	Min throughput per process 			=  472256.50 KB/sec 
	Max throughput per process 			=  473656.00 KB/sec
	Avg throughput per process 			=  472956.25 KB/sec
	Min xfer 					=  130672.00 KB

	Children see throughput for  2 readers 		= 1889937.50 KB/sec
	Parent sees throughput for  2 readers 		=   77196.49 KB/sec
	Min throughput per process 			=  944327.38 KB/sec 
	Max throughput per process 			=  945610.12 KB/sec
	Avg throughput per process 			=  944968.75 KB/sec
	Min xfer 					=  130948.00 KB

	Children see throughput for 2 re-readers 	= 1888540.12 KB/sec
	Parent sees throughput for 2 re-readers 	= 1882104.77 KB/sec
	Min throughput per process 			=  942036.19 KB/sec 
	Max throughput per process 			=  946503.94 KB/sec
	Avg throughput per process 			=  944270.06 KB/sec
	Min xfer 					=  130456.00 KB


	Each process writes a 131072 Kbyte file in 4 Kbyte records

	Children see throughput for  3 initial writers 	=  644641.47 KB/sec
	Parent sees throughput for  3 initial writers 	=    1424.12 KB/sec
	Min throughput per process 			=  187386.69 KB/sec 
	Max throughput per process 			=  269646.66 KB/sec
	Avg throughput per process 			=  214880.49 KB/sec
	Min xfer 					=   91084.00 KB

	Children see throughput for  3 rewriters 	= 1004588.22 KB/sec
	Parent sees throughput for  3 rewriters 	=   58914.05 KB/sec
	Min throughput per process 			=  275948.25 KB/sec 
	Max throughput per process 			=  445058.56 KB/sec
	Avg throughput per process 			=  334862.74 KB/sec
	Min xfer 					=   81280.00 KB

	Children see throughput for  3 readers 		= 2166543.88 KB/sec
	Parent sees throughput for  3 readers 		= 1460932.53 KB/sec
	Min throughput per process 			=  619224.88 KB/sec 
	Max throughput per process 			=  922048.94 KB/sec
	Avg throughput per process 			=  722181.29 KB/sec
	Min xfer 					=   86596.00 KB

	Children see throughput for 3 re-readers 	= 2138529.88 KB/sec
	Parent sees throughput for 3 re-readers 	= 2130352.73 KB/sec
	Min throughput per process 			=  616222.00 KB/sec 
	Max throughput per process 			=  903646.56 KB/sec
	Avg throughput per process 			=  712843.29 KB/sec
	Min xfer 					=   89388.00 KB


	Each process writes a 131072 Kbyte file in 4 Kbyte records

	Children see throughput for  4 initial writers 	=  612325.26 KB/sec
	Parent sees throughput for  4 initial writers 	=   34747.37 KB/sec
	Min throughput per process 			=  125476.16 KB/sec 
	Max throughput per process 			=  207964.28 KB/sec
	Avg throughput per process 			=  153081.31 KB/sec
	Min xfer 					=   77176.00 KB

	Children see throughput for  4 rewriters 	=  238829.30 KB/sec
	Parent sees throughput for  4 rewriters 	=   42411.91 KB/sec
	Min throughput per process 			=   48757.11 KB/sec 
	Max throughput per process 			=   71481.82 KB/sec
	Avg throughput per process 			=   59707.32 KB/sec
	Min xfer 					=  113220.00 KB

	Children see throughput for  4 readers 		= 2380958.56 KB/sec
	Parent sees throughput for  4 readers 		= 1638434.75 KB/sec
	Min throughput per process 			=  582672.88 KB/sec 
	Max throughput per process 			=  602259.06 KB/sec
	Avg throughput per process 			=  595239.64 KB/sec
	Min xfer 					=  126828.00 KB

	Children see throughput for 4 re-readers 	= 2406015.31 KB/sec
	Parent sees throughput for 4 re-readers 	= 2389809.41 KB/sec
	Min throughput per process 			=  590431.31 KB/sec 
	Max throughput per process 			=  616499.38 KB/sec
	Avg throughput per process 			=  601503.83 KB/sec
	Min xfer 					=  124800.00 KB



iozone test complete.
I'm having significant performance issues but want to understand the report better so that I can start running tests to diagnose. First and foremost, how come in some instances the "Parent Sees" throughput can be half to 1/300th of the child throughput. I'm able to repeat this a lot, what should I be looking for to understand this?

Note that the system is not doing anything else but the iozone test.

I've been through the source code a little to see that the parent just looks at the overall data moved of all the children divided by the program run time vs the child throughput which is the sum of all the children's individually calculated throughputs. I'm surprised to see the parent always significantly lower than the children.

Appreciate any pointers here.