File size: 1,819 Bytes
45b811b | 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 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 | #include <iostream>
#include <string>
#include <cstdlib>
#include <sys/mman.h>
#include <unistd.h>
#include <cstring>
int main(int argc, char** argv) {
if (argc != 2) {
std::cerr << "Usage: " << argv[0] << " <GB to allocate and lock>\n";
return 1;
}
double gb = std::stod(argv[1]);
size_t bytes = static_cast<size_t>(gb * 1024.0 * 1024.0 * 1024.0);
std::cout << "Allocating " << gb << " GB (" << bytes << " bytes) of RAM...\n";
void* ptr = mmap(NULL, bytes, PROT_READ | PROT_WRITE, MAP_PRIVATE | MAP_ANONYMOUS, -1, 0);
if (ptr == MAP_FAILED) {
perror("mmap failed");
return 1;
}
std::cout << "Memory allocated. Faulting pages and pinning to RAM...\n";
// Write to memory to map it to physical pages and prevent lazy allocation
size_t page_size = sysconf(_SC_PAGESIZE);
char* char_ptr = static_cast<char*>(ptr);
for (size_t i = 0; i < bytes; i += page_size) {
char_ptr[i] = 1;
}
// Mlock to pin it to RAM and prevent it from being swapped out itself
if (mlock(ptr, bytes) != 0) {
perror("mlock failed (you probably need to run with sudo)");
} else {
std::cout << "mlock successful.\n";
}
std::cout << "Memory is fully resident. Other inactive processes/caches should be pushed to swap.\n";
std::cout << "Clearing filesystem caches...\n";
int ret = system("echo 3 | sudo tee /proc/sys/vm/drop_caches > /dev/null");
if (ret != 0) {
std::cerr << "Failed to clear caches. (Maybe sudo failed?)\n";
} else {
std::cout << "Caches cleared successfully.\n";
}
std::cout << "Unlocking and releasing memory...\n";
munlock(ptr, bytes);
munmap(ptr, bytes);
std::cout << "Done! Try starting your model now.\n";
return 0;
}
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