1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
|
#include <fcntl.h>
#include <unistd.h>
#include <cstdlib>
#include <thread>
#include <vector>
int fd;
void read_from_offset(int off) {
const int buffer_size = 10000;
char buffer[buffer_size];
if (pread(fd, buffer, sizeof(buffer), off) == -1) {
exit(1);
}
}
int main(int argc, char* argv[]) {
if (argc < 2) {
return 2;
}
fd = open(argv[1], O_RDONLY);
if (fd == -1) {
return 1;
}
std::vector<std::thread> threads;
int count = 4;
const int interval = 30000;
for (int off = 0; off < count * interval; off += interval) {
threads.emplace_back(read_from_offset, off);
}
for (auto& t : threads) {
t.join();
}
close(fd);
return 0;
}
|
