PERFORCE change 166362 for review

[Zhao Shuai]

http://perforce.freebsd.org/chv.cgi?CH=166362

Change 166362 by zhaoshuai at zhaoshuai on 2009/07/21 13:25:06

	add LMbench result

Affected files ...

.. //depot/projects/soc2009/fifo/fifo_test/README#3 edit

Differences ...

==== //depot/projects/soc2009/fifo/fifo_test/README#3 (text+ko) ====

@@ -57,7 +57,7 @@
 	
 	The test is executed 100 times for all combinations of the following 
 	parameters for message size and number of messages transmitted. The 
-	avarage time is caculated and then printed.
+	avarage time cost is caculated and then printed.
 	    - Message size(bytes): 64, 128, 256, 512, 1024, 2048, 4096
 	    - Number of messages : 100, 1000, 5000, 10000, 100000
 
@@ -91,10 +91,50 @@
 
 	From these results, we can see that the new fifo implementation gains little
 	advantage over the old fifo implementation when transfering small amount of data.
-	e.g. transferring 100*128 bytes of data costs 89 microseconds under the new fifo 
-	code while it costs 96 microseconds under the old fifo code. But when transferring 
+	e.g. handling 100*128 bytes of data costs 89 microseconds under the new fifo code 
+	while it costs 96 microseconds under the old fifo code. But when transferring 
 	large amount of data, the new fifo implementation gains significant advantage over
-	the old fifo implementation. e.g. it takes 1126 microseconds transferring 10000*64 
+	the old fifo implementation. e.g. it takes 1126 microseconds handling 10000*64 
 	bytes of data under the old fifo implementation, but under the new fifo implementation,
 	it takes 753 microseconds, saving 30% of time. That is to say, the new fifo system
 	increases the throughput by 30% in this case.
+
+	== LMbench ==
+
+	There is a FIFO related test in LMBench. It is designed to measure FIFO latency.
+	I run the test many times, but the result varies from time to time. 
+
+	Here are 10 results observed under the new fifo implementation.
+
+		FIFO latency: 12.2243 microseconds
+		FIFO latency: 12.1555 microseconds
+		FIFO latency: 16.0318 microseconds
+		FIFO latency: 16.4396 microseconds
+		FIFO latency: 14.5265 microseconds
+		FIFO latency: 15.3577 microseconds
+		FIFO latency: 7.5029 microseconds
+		FIFO latency: 12.9248 microseconds
+		FIFO latency: 13.6932 microseconds
+		FIFO latency: 11.6913 microseconds
+	
+	The following 10 results are observed under the old fifo implementation.
+
+		FIFO latency: 11.8956 microseconds
+		FIFO latency: 10.2409 microseconds
+		FIFO latency: 10.8170 microseconds
+		FIFO latency: 9.4636 microseconds
+		FIFO latency: 18.8605 microseconds
+		FIFO latency: 5.7682 microseconds
+		FIFO latency: 6.9138 microseconds
+		FIFO latency: 5.6443 microseconds
+		FIFO latency: 15.9345 microseconds
+		FIFO latency: 7.4886 microseconds
+
+	It is very strange that the result fluctuates in a large range. Since each value
+	we get is an avarage value which is caculated after hundreds of internal test, 
+	we could expect that each result have little difference with others.
+	
+	I think the testing method adopted by LMbench is not stable, thus those results 
+	are not convincing.
+
+