Implement GetCPUUsage; it was causing link errors because of its absence on t...

base/process_util_posix.cc

Index: base/process_util_posix.cc
===================================================================
--- base/process_util_posix.cc	(revision 6214)
+++ base/process_util_posix.cc	(working copy)
@@ -4,12 +4,17 @@
 
 #include "base/process_util.h"
 
+#include <sys/resource.h>
+#include <sys/time.h>
 #include <sys/types.h>
 #include <unistd.h>
 
 #include "base/basictypes.h"
+#include "base/logging.h"
 #include "base/sys_info.h"
 
+const int kMicrosecondsPerSecond = 1000000;
+
 namespace base {
 
 int GetCurrentProcId() {
@@ -46,4 +51,52 @@
   // setpriority() or sched_getscheduler, but these all require extra rights.
 }
 
+namespace {
+
+int64 TimeValToMicroseconds(const struct timeval& tv) {
+  return tv.tv_sec * kMicrosecondsPerSecond + tv.tv_usec;
+}
+
+}
+
+int ProcessMetrics::GetCPUUsage() {
+  int retval;

[pink (ping after 24hrs), 2008/12/02 19:36:11]

declare retval where it's initialized or give it an initial value.

+  struct timeval now;
+  struct rusage usage;
+
+  retval = gettimeofday(&now, NULL);
+  if (retval)
+    return 0;
+  retval = getrusage(RUSAGE_SELF, &usage);
+  if (retval)
+    return 0;
+  
+  int64 system_time = (TimeValToMicroseconds(usage.ru_stime) +
+                       TimeValToMicroseconds(usage.ru_utime)) /
+                        processor_count_;

[pink (ping after 24hrs), 2008/12/02 19:36:11]

does |processor_count_| get scaled to an int64 or do the other values get scaled
down to 32bits? just making sure.

[Avi (use Gerrit), 2008/12/02 19:40:31]

I'm pretty sure int64/int32 causes the int32 to be promoted.

+  int64 time = TimeValToMicroseconds(now);
+
+  if ((last_system_time_ == 0) || (last_time_ == 0)) {

[pink (ping after 24hrs), 2008/12/02 19:36:11]

don't need the extra parens, but not a biggie.

[Avi (use Gerrit), 2008/12/02 19:40:31]

Straight from the Windows code.

+    // First call, just set the last values.
+    last_system_time_ = system_time;
+    last_time_ = time;
+    return 0;
+  }
+
+  int64 system_time_delta = system_time - last_system_time_;
+  int64 time_delta = time - last_time_;
+  DCHECK(time_delta != 0);
+  if (time_delta == 0)
+    return 0;
+
+  // We add time_delta / 2 so the result is rounded.
+  int cpu = static_cast<int>((system_time_delta * 100 + time_delta / 2) /
+                             time_delta);
+
+  last_system_time_ = system_time;
+  last_time_ = time;
+
+  return cpu;
+}
+
 }  // namespace base