repro.cpp

/* SPDX-License-Identifier: GPL-2.0-only */
#include <stdexcept>
#include <benchmark/benchmark.h>

#include <sys/mman.h>

static void mprotect_bench(benchmark::State& state)
{
	int i = 0;
	void *ptr;
	size_t size = 40000 * 1024;

	ptr = mmap(NULL, size, PROT_READ | PROT_WRITE, MAP_ANONYMOUS | MAP_PRIVATE, -1, 0);
	if (ptr == MAP_FAILED)
		throw std::runtime_error("ohno");
	madvise(ptr, size, MADV_NOHUGEPAGE);
	madvise(ptr, size, MADV_POPULATE_WRITE);
	for (auto _ : state) {
		if (i & 1)
			mprotect(ptr, size, PROT_NONE);
		else
			mprotect(ptr, size, PROT_READ | PROT_WRITE);
		i++;
	}
}
BENCHMARK(mprotect_bench);
BENCHMARK_MAIN();