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// Copyright 2020 The gVisor Authors.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
#include <stdlib.h>
#include <sys/mman.h>
#include <unistd.h>
#include "gtest/gtest.h"
#include "benchmark/benchmark.h"
#include "test/util/logging.h"
#include "test/util/memory_util.h"
#include "test/util/posix_error.h"
#include "test/util/test_util.h"
namespace gvisor {
namespace testing {
namespace {
// Conservative value for /proc/sys/vm/max_map_count, which limits the number of
// VMAs, minus a safety margin for VMAs that already exist for the test binary.
// The default value for max_map_count is
// include/linux/mm.h:DEFAULT_MAX_MAP_COUNT = 65530.
constexpr size_t kMaxVMAs = 64001;
// Map then unmap pages without touching them.
void BM_MapUnmap(benchmark::State& state) {
// Number of pages to map.
const int pages = state.range(0);
while (state.KeepRunning()) {
void* addr = mmap(0, pages * kPageSize, PROT_READ | PROT_WRITE,
MAP_PRIVATE | MAP_ANONYMOUS, -1, 0);
TEST_CHECK_MSG(addr != MAP_FAILED, "mmap failed");
int ret = munmap(addr, pages * kPageSize);
TEST_CHECK_MSG(ret == 0, "munmap failed");
}
}
BENCHMARK(BM_MapUnmap)->Range(1, 1 << 17)->UseRealTime();
// Map, touch, then unmap pages.
void BM_MapTouchUnmap(benchmark::State& state) {
// Number of pages to map.
const int pages = state.range(0);
while (state.KeepRunning()) {
void* addr = mmap(0, pages * kPageSize, PROT_READ | PROT_WRITE,
MAP_PRIVATE | MAP_ANONYMOUS, -1, 0);
TEST_CHECK_MSG(addr != MAP_FAILED, "mmap failed");
char* c = reinterpret_cast<char*>(addr);
char* end = c + pages * kPageSize;
while (c < end) {
*c = 42;
c += kPageSize;
}
int ret = munmap(addr, pages * kPageSize);
TEST_CHECK_MSG(ret == 0, "munmap failed");
}
}
BENCHMARK(BM_MapTouchUnmap)->Range(1, 1 << 17)->UseRealTime();
// Map and touch many pages, unmapping all at once.
//
// NOTE(b/111429208): This is a regression test to ensure performant mapping and
// allocation even with tons of mappings.
void BM_MapTouchMany(benchmark::State& state) {
// Number of pages to map.
const int page_count = state.range(0);
while (state.KeepRunning()) {
std::vector<void*> pages;
for (int i = 0; i < page_count; i++) {
void* addr = mmap(nullptr, kPageSize, PROT_READ | PROT_WRITE,
MAP_PRIVATE | MAP_ANONYMOUS, -1, 0);
TEST_CHECK_MSG(addr != MAP_FAILED, "mmap failed");
char* c = reinterpret_cast<char*>(addr);
*c = 42;
pages.push_back(addr);
}
for (void* addr : pages) {
int ret = munmap(addr, kPageSize);
TEST_CHECK_MSG(ret == 0, "munmap failed");
}
}
state.SetBytesProcessed(kPageSize * page_count * state.iterations());
}
BENCHMARK(BM_MapTouchMany)->Range(1, 1 << 12)->UseRealTime();
void BM_PageFault(benchmark::State& state) {
// Map the region in which we will take page faults. To ensure that each page
// fault maps only a single page, each page we touch must correspond to a
// distinct VMA. Thus we need a 1-page gap between each 1-page VMA. However,
// each gap consists of a PROT_NONE VMA, instead of an unmapped hole, so that
// if there are background threads running, they can't inadvertently creating
// mappings in our gaps that are unmapped when the test ends.
size_t test_pages = kMaxVMAs;
// Ensure that test_pages is odd, since we want the test region to both
// begin and end with a mapped page.
if (test_pages % 2 == 0) {
test_pages--;
}
const size_t test_region_bytes = test_pages * kPageSize;
// Use MAP_SHARED here because madvise(MADV_DONTNEED) on private mappings on
// gVisor won't force future sentry page faults (by design). Use MAP_POPULATE
// so that Linux pre-allocates the shmem file used to back the mapping.
Mapping m = ASSERT_NO_ERRNO_AND_VALUE(
MmapAnon(test_region_bytes, PROT_READ, MAP_SHARED | MAP_POPULATE));
for (size_t i = 0; i < test_pages / 2; i++) {
ASSERT_THAT(
mprotect(reinterpret_cast<void*>(m.addr() + ((2 * i + 1) * kPageSize)),
kPageSize, PROT_NONE),
SyscallSucceeds());
}
const size_t mapped_pages = test_pages / 2 + 1;
// "Start" at the end of the mapped region to force the mapped region to be
// reset, since we mapped it with MAP_POPULATE.
size_t cur_page = mapped_pages;
for (auto _ : state) {
if (cur_page >= mapped_pages) {
// We've reached the end of our mapped region and have to reset it to
// incur page faults again.
state.PauseTiming();
ASSERT_THAT(madvise(m.ptr(), test_region_bytes, MADV_DONTNEED),
SyscallSucceeds());
cur_page = 0;
state.ResumeTiming();
}
const uintptr_t addr = m.addr() + (2 * cur_page * kPageSize);
const char c = *reinterpret_cast<volatile char*>(addr);
benchmark::DoNotOptimize(c);
cur_page++;
}
}
BENCHMARK(BM_PageFault)->UseRealTime();
} // namespace
} // namespace testing
} // namespace gvisor
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