Add support for CountResidentBytes in windows

base/trace_event/process_memory_dump.cc

Index: base/trace_event/process_memory_dump.cc
diff --git a/base/trace_event/process_memory_dump.cc b/base/trace_event/process_memory_dump.cc
index ae60bb06b152639c0e80ab2226a6a96b65699351..19cc05471a90db3aef8137e4d1ae3eb7d10e35ba 100644
--- a/base/trace_event/process_memory_dump.cc
+++ b/base/trace_event/process_memory_dump.cc
@@ -16,6 +16,10 @@
 #include <sys/mman.h>
 #endif
 
+#if defined(OS_WIN)
+#include <Psapi.h>
+#endif
+
 namespace base {
 namespace trace_event {
 
@@ -45,9 +49,9 @@ size_t ProcessMemoryDump::CountResidentBytes(void* start_address,
   const size_t kMaxChunkSize = 32 * 1024 * 1024;
   size_t offset = 0;
   size_t total_resident_size = 0;
-  int result = 0;
+  int result = 0;  // 0 on success.
   while (offset < mapped_size) {
-    void* chunk_start = reinterpret_cast<void*>(start_pointer + offset);
+    uintptr_t chunk_start = (start_pointer + offset);
     const size_t chunk_size = std::min(mapped_size - offset, kMaxChunkSize);
     const size_t page_count = (chunk_size + page_size - 1) / page_size;
     size_t resident_page_count = 0;
@@ -55,18 +59,33 @@ size_t ProcessMemoryDump::CountResidentBytes(void* start_address,
 #if defined(OS_MACOSX) || defined(OS_IOS)
     std::vector<char> vec(page_count + 1);
     // mincore in MAC does not fail with EAGAIN.
-    result = mincore(chunk_start, chunk_size, vec.data());
+    result =
+        mincore(reinterpret_cast<void*>(chunk_start), chunk_size, vec.data());
     if (result)
       break;
 
     for (size_t i = 0; i < page_count; i++)
       resident_page_count += vec[i] & MINCORE_INCORE ? 1 : 0;
+#elif defined(OS_WIN)
+    std::vector<PSAPI_WORKING_SET_EX_INFORMATION> vec(page_count + 1);

[brucedawson, 2016/01/19 19:39:08]

Why is there a "+ 1" here?

[ssid, 2016/01/19 19:58:16]

I was anticipating to count for non-aligned memory, so i added 1 for extra. This
shouldn't be here.

+    for (size_t i = 0; i < page_count; i++) {
+      vec[i].VirtualAddress =
+          reinterpret_cast<void*>(chunk_start + i * page_size);
+    }
+    DWORD vec_size = static_cast<DWORD>(
+        page_count * sizeof(PSAPI_WORKING_SET_EX_INFORMATION));
+    result = !QueryWorkingSetEx(GetCurrentProcess(), vec.data(), vec_size);
+    if (result)
+      break;
+    for (size_t i = 0; i < page_count; i++)
+      resident_page_count += vec[i].VirtualAttributes.Valid;

[brucedawson, 2016/01/19 19:39:08]

I *think* this is correct, but the documentation is not entirely explicit about
what "Valid" really means. That is, it doesn't directly say whether that means
that the page is in the working set of the process, but I think it must.

[ssid, 2016/01/19 19:58:16]

Yes, I had the same doubt. So, I tried experimenting using the patch and it gave
me Valid only on pages I used. Also Since the api name is
PSAPI_WORKING_SET_EX_INFORMATION, it gives me more confidence that the page is
valid only if it's part of working set.

 #else   // defined(OS_MACOSX) || defined(OS_IOS)
     std::vector<unsigned char> vec(page_count + 1);
     int error_counter = 0;
     // HANDLE_EINTR tries for 100 times. So following the same pattern.
     do {
-      result = mincore(chunk_start, chunk_size, vec.data());
+      result =
+          mincore(reinterpret_cast<void*>(chunk_start), chunk_size, vec.data());
     } while (result == -1 && errno == EAGAIN && error_counter++ < 100);
     if (result)
       break;