1 /*
2 * Copyright (C) 2010 The Android Open Source Project
3 *
4 * Licensed under the Apache License, Version 2.0 (the "License");
5 * you may not use this file except in compliance with the License.
6 * You may obtain a copy of the License at
7 *
8 * http://www.apache.org/licenses/LICENSE-2.0
9 *
10 * Unless required by applicable law or agreed to in writing, software
11 * distributed under the License is distributed on an "AS IS" BASIS,
12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13 * See the License for the specific language governing permissions and
14 * limitations under the License.
15 */
16
17 #include <stdio.h>
18 #include <stdlib.h>
19 #include <stdint.h>
20 #include <unistd.h>
21 #include <sys/time.h>
22 #include <time.h>
23
24 #define N_PAGES (4096)
25
26 #define WARMUP (1<<10)
27
28 #define WORKLOAD (1<<24)
29
30 int numPagesList[] = {
31 1, 2, 3, 4, 5, 6, 7, 8, 9, 10,
32 12, 14, 16, 18, 20, 24, 28, 30, 32, 34, 48, 62, 64, 66, 80,
33 96, 112, 128, 144, 160, 320, 480, 496, 512, 528, 544, 576, 640, 960,
34 1024, 2048, 3072, 4000,
35 };
36
stop_watch()37 static unsigned long long stop_watch()
38 {
39 struct timespec t;
40 t.tv_sec = t.tv_nsec = 0;
41 clock_gettime(CLOCK_MONOTONIC, &t);
42 return t.tv_sec*1000000000ULL + t.tv_nsec;
43 }
44
main()45 int main()
46 {
47 char *mem = malloc((N_PAGES+1) * 4096);
48 intptr_t *p;
49 int i;
50 unsigned int j;
51
52 /* Align to page start */
53 mem = (char *) ((intptr_t) (mem + 4096) & ~0xfff);
54
55 for (j = 0; j < sizeof(numPagesList)/sizeof(int); j++) {
56 int numPages = numPagesList[j];
57 int pageIdx = 0;
58 int entryOffset = 0;
59
60 /*
61 * page 0 page 1 page 2 .... page N
62 * ------ ------ ------ ------
63 * word 0 -> word 0 -> word 0 -> .... -> word 0 -> (page 0/word 0)
64 * : : : : :
65 * word 1023 word 1023 word 1023 : word 1023
66 */
67 for (i = 0; i < numPages; i++) {
68 int nextPageIdx = (pageIdx + 1) % numPages;
69 /* Looks like spread the pointer across cache lines introduce noise
70 * to get to the asymptote
71 * int nextEntryOffset = (entryOffset + 32) % 1024;
72 */
73 int nextEntryOffset = entryOffset;
74
75 if (i != numPages -1) {
76 *(intptr_t *) (mem + 4096 * pageIdx + entryOffset) =
77 (intptr_t) (mem + 4096 * nextPageIdx + nextEntryOffset);
78 } else {
79 /* Last page - form the cycle */
80 *(intptr_t *) (mem + 4096 * pageIdx + entryOffset) =
81 (intptr_t) &mem[0];
82 }
83
84 pageIdx = nextPageIdx;
85 entryOffset = nextEntryOffset;
86 }
87
88 /* Starting point of the pointer chase */
89 p = (intptr_t *) &mem[0];
90
91 /* Warmup (ie pre-thrash the memory system */
92 for (i = 0; i < WARMUP; i++) {
93 p = (intptr_t *) *p;
94 }
95
96 /* Real work */
97 unsigned long long t0 = stop_watch();
98 for (i = 0; i < WORKLOAD; i++) {
99 p = (intptr_t *) *p;
100 }
101 unsigned long long t1 = stop_watch();
102
103 /* To keep p from being optimized by gcc */
104 if (p)
105 printf("%d, %f\n", numPages, (float) (t1 - t0) / WORKLOAD);
106 }
107 return 0;
108 }
109