tsan: fix and make faster GetRSS

It is currently broken because it reads a wrong value from profile (heap instead of total).
Also make it faster by reading /proc/self/statm. Reading of /proc/self/smaps
can consume more than 50% of time on beefy apps if done every 100ms.

llvm-svn: 213942

compiler-rt/lib/tsan/rtl/tsan_platform_linux.cc

@@ -109,9 +109,30 @@ void WriteMemoryProfile(char *buf, uptr buf_size, uptr nthread, uptr nlive) {
 }
 
 uptr GetRSS() {
-  uptr mem[7] = {};
-  __sanitizer::GetMemoryProfile(FillProfileCallback, mem, 7);
-  return mem[6];
+  uptr fd = OpenFile("/proc/self/statm", false);
+  if ((sptr)fd < 0)
+    return 0;
+  char buf[64];
+  uptr len = internal_read(fd, buf, sizeof(buf) - 1);
+  internal_close(fd);
+  if ((sptr)len <= 0)
+    return 0;
+  buf[len] = 0;
+  // The format of the file is:
+  // 1084 89 69 11 0 79 0
+  // We need the second number which is RSS in 4K units.
+  char *pos = buf;
+  // Skip the first number.
+  while (*pos >= '0' && *pos <= '9')
+    pos++;
+  // Skip whitespaces.
+  while (!(*pos >= '0' && *pos <= '9') && *pos != 0)
+    pos++;
+  // Read the number.
+  uptr rss = 0;
+  while (*pos >= '0' && *pos <= '9')
+    rss = rss * 10 + *pos++ - '0';
+  return rss * 4096;
 }
 
 #if SANITIZER_LINUX