|
Garbage Collection
Part:
1
2
3
4
5
6
7
8
9
(Continued from previous part...)
Note that
- An inner class MyObject is used to represent a generic object.
It has a fixed size of 128KB plus some overhead.
- Another inner class MyList is used to as a manager to register
and release objects. It uses a linked list data structure to do the job.
- A third inner class Monitor is used to sample memory usage and object
counts data.
- The main test, myTest(), is divided two sections: the initialization
section, where a number of objects are added to the list; the loop section,
where objects are added to the list, then removed from the list.
- Two paramters are supported. The first one, initSteps, is used to
control how many objects we want to put into the list initially. The second
one, testSteps, is used to control the number objects to be added to the list
before removing the same number of objects from the list.
- Two types of data are collected by the program: memory usage data, including
total memory, free memory, and the percentage of the free memory over total memory;
and counts of my objects, including number of total object, number of active
objects, and number of dead objects. The object counts have been converted into
memory sizes to make it easier to compare them with memory usages.
- Memory related data has been normalized into kilo bytes (BK).
- The over head memory represents the memory that are used by the program, but
not by the allocated objects.
GCTest Program Output - Constant Memory Requirement
I compiled GCTest.java with J2SDK 1.4.0_02, and executed it with:
java -Xms2m -Xmx8m GCTest 16 1 > tail_16_01.out
I got the following output:
Time Total Free Free Total Act. Dead Over
sec. Mem. Mem. Per. Obj. Obj. Obj. Head
0 1984 1727 87% 0 0 0 257
0 1984 1593 80% 128 128 0 263
1 1984 1592 80% 128 128 0 264
1 1984 1462 73% 256 256 0 266
2 1984 1332 67% 384 384 0 268
2 1984 1202 60% 512 512 0 270
....
8 3124 1062 33% 1920 1920 0 142
8 3124 932 29% 2048 2048 0 144
9 3124 803 25% 2176 2176 0 145
9 3124 801 25% 2176 2048 128 147
10 3124 671 21% 2304 2176 128 149
10 3124 669 21% 2304 2048 256 151
11 3124 540 17% 2432 2176 256 152
11 3124 538 17% 2432 2048 384 154
12 3124 408 13% 2560 2176 384 156
12 3124 406 12% 2560 2048 512 158
13 3124 277 8% 2688 2176 512 159
13 3124 275 8% 2688 2048 640 161
14 5256 2303 43% 2176 2176 0 777
14 5256 2301 43% 2176 2048 128 779
15 5256 2171 41% 2304 2176 128 781
15 5256 2170 41% 2304 2048 256 782
16 5256 2040 38% 2432 2176 256 784
16 5256 2038 38% 2432 2048 384 786
....
29 5256 330 6% 4096 2176 1920 830
29 5256 329 6% 4096 2048 2048 831
30 5256 199 3% 4224 2176 2048 833
30 5256 197 3% 4224 2048 2176 835
31 7848 3358 42% 2176 2176 0 2314
31 7848 3357 42% 2176 2048 128 2315
32 7848 3227 41% 2304 2176 128 2317
32 7848 3225 41% 2304 2048 256 2319
33 7848 3095 39% 2432 2176 256 2321
33 7848 3094 39% 2432 2048 384 2322
....
54 7848 334 4% 5120 2176 2944 2394
55 7848 332 4% 5120 2048 3072 2396
55 7848 203 2% 5248 2176 3072 2397
56 7848 201 2% 5248 2048 3200 2399
56 8128 2614 32% 2176 2176 0 3338
57 8128 2612 32% 2176 2048 128 3340
57 8128 2482 30% 2304 2176 128 3342
58 8128 2481 30% 2304 2048 256 3343
58 8128 2351 28% 2432 2176 256 3345
59 8128 2349 28% 2432 2048 384 3347
....
73 8128 378 4% 4352 2176 2176 3398
74 8128 377 4% 4352 2048 2304 3399
74 8128 247 3% 4480 2176 2304 3401
75 8128 245 3% 4480 2048 2432 3403
75 8128 3382 41% 2176 2176 0 2570
76 8128 3381 41% 2176 2048 128 2571
76 8128 3251 39% 2304 2176 128 2573
77 8128 3249 39% 2304 2048 256 2575
77 8128 3119 38% 2432 2176 256 2577
78 8128 3118 38% 2432 2048 384 2578
....
98 8128 358 4% 5120 2176 2944 2650
99 8128 356 4% 5120 2048 3072 2652
99 8128 226 2% 5248 2176 3072 2654
100 8128 225 2% 5248 2048 3200 2655
100 8128 2614 32% 2176 2176 0 3338
101 8128 2612 32% 2176 2048 128 3340
101 8128 2482 30% 2304 2176 128 3342
102 8128 2481 30% 2304 2048 256 3343
102 8128 2351 28% 2432 2176 256 3345
103 8128 2349 28% 2432 2048 384 3347
....
117 8128 378 4% 4352 2176 2176 3398
118 8128 376 4% 4352 2048 2304 3400
118 8128 247 3% 4480 2176 2304 3401
119 8128 245 3% 4480 2048 2432 3403
119 8128 3382 41% 2176 2176 0 2570
120 8128 3380 41% 2176 2048 128 2572
120 8128 3251 39% 2304 2176 128 2573
121 8128 3249 39% 2304 2048 256 2575
121 8128 3119 38% 2432 2176 256 2577
122 8128 3117 38% 2432 2048 384 2579
(Continued on next part...)
Part:
1
2
3
4
5
6
7
8
9
| 