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CPU OVERHEAD II
Data
(fixed time)
Last Modified:  23 May 2001

Below is the test data taken relative to CPU overhead.

Cost to user per interrupt in nanoseconds:
    average:           11,542
    sample STD:         987
    NOTE - If data set 1 is thrown out then the costs are
    average:           11,354
    sample STD:         499
 

 
<--
INTERRUPTS
                                              -->
AVG TESTCYCLES++
AVG COST PER
DATA SET
TIME BETWEEN* (ns)
TARGET NUMBER**
ACTUAL NUMBER&
PER TIMING RUN&&
INTERRUPT
0
--
0
0
0.101794 #
--
1
300,600 [600]
234,000
233,922 
 0.0966163
15,290
2
275,550 [550]
254,000
253,869 
 0.097479
11,680
3
250,500 [500]
280,000
 279,941
 0.0973673
10,893
4
225,450 [450]
311,000
 309,937
 0.0960345
12,756
5
200,400 [400]
350,000
 347,505
 0.0955419
12,308
6
175,350 [350]
400,000
 397,045
0.0951524
11,441
7
150,300 [300]
466,000
 463,780
 0.0942383
11,156
8
125,250 [250]
559,000
 552,470
 0.0919225
12,146
9
100,200 [200]
699,000
 694,502
 0.0902618
11,352
10
75,150 [150]
932,000
 924,559
 0.086545
11,258
11
50100 [100]
1,398,000
 1,385,551
 0.0794026
11,020
12
45,090 [90]
1,553,000
 1,524,719
 0.0767495
11,094
13
40,080 [80]
1,747,000
 1,728,965
 0.0735660
11,114
14
35,070 [70]
1,996,000
 1,979,034
 0.0694943
11,128
15
32,565 [65]
2,150,000
 2,118,327
0.0668026 
11,194
16
30,060 [60]
2,330,000
 2,296,655
 0.0636523
11,263
17
27,555 [55]
2,550,000
 2,522,154
 0.0607554
11,109
18
25,050 [50]
2,800,000
 2,794,888
0.0567606 
11,082
19
22,545 [45]
3,105,000
 3,068,269
 0.0515024
11,138
20
 22,040 [40]
3,177,000
3,161,938
0.047058
10,776
21
17,535 [35]
3,993,000
3,938,972
0.036874
11,183

*       "TIME BETWEEN" is based on 501 nanoseconds per Myrinet card RTC unit.  So it is (RTC units) * 501.   Number in "[ ]" is the RTC units.
**    "TARGET NUMBER" should achieve 70 seconds of interrupts.
&     "ACTUAL NUMBER" is checked using "procinfo" to ensure interrupt stream did not hang.
&&  Nine runs of seven seconds each.  First run is not counted in average.
+      First run is thrown out.
++   A "TESTCYCLE" is a count of the number of cycles of the inner for-loop as a fraction of 2^32 (so that inner and outer loops may be combined into one number).
@    Based on before and after cpu usage using the getrusage  and gettimeofday utilities, this value corresponds to 100% user time.
 
 



Bill Lawry