mprotect benchmarks

mprotect_bench.c

#include <stdlib.h>
#include <stdio.h>
#include <stdint.h>
#include <time.h>
#include <unistd.h>
#include <sys/mman.h>

#define SIZE (1ull<<35) // 32GB
#define N (SIZE/sizeof(uint64_t))
#define NTIMES 100

void initialize(uint64_t *a, size_t size) {
	printf("initializing... ");
	fflush(stdout);
	clock_t start = clock();
	a[0] = 123;
	for (size_t i=1; i < size; i++) {
		a[i] = a[i-1] * a[i-1] % 100000;
	}
	clock_t end = clock();
	double seconds = (double)(end - start) / CLOCKS_PER_SEC;
	printf("done in %lf seconds\n", seconds);
}

void time_mprotect(void *addr, size_t size, size_t ntimes) {
	clock_t start = clock();
	for (size_t i=0; i < ntimes; i++) {
		if (mprotect(addr, size, PROT_READ) == -1) {
			perror("mprotect failed");
			exit(-1);
		}
		if (mprotect(addr, size, PROT_READ | PROT_WRITE) == -1) {
			perror("mprotect failed");
			exit(-1);
		}
	}
	clock_t end = clock();
	double seconds = (double)(end - start) / CLOCKS_PER_SEC;
	printf("mprotect %zuKB -> %lf seconds\n", size/1024, seconds/ntimes);
}

int main() {
	uint64_t *a = mmap(NULL, N * sizeof(uint64_t), PROT_READ | PROT_WRITE,
	                   MAP_SHARED | MAP_ANONYMOUS, -1, 0);
	long pagesize = sysconf(_SC_PAGESIZE);
	initialize(a, N);
	for(uint64_t i = pagesize; i <= SIZE; i *= 2) {
		time_mprotect(a, i, NTIMES);
	}
	return 0;
}