Add basic microbenchmarks.

PiperOrigin-RevId: 296104390

1 files changed, 163 insertions, 0 deletions

diff --git a/test/perf/linux/mapping_benchmark.cc b/test/perf/linux/mapping_benchmark.cc
new file mode 100644
index 000000000..39c30fe69
--- /dev/null
+++ b/test/perf/linux/mapping_benchmark.cc
@@ -0,0 +1,163 @@
+// 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