Provide a port of cpu related code to posix, and linux.

Properly set this up in our build environment.
	Change on 2014/12/23 by ctiller <ctiller@google.com>
-------------
Created by MOE: http://code.google.com/p/moe-java
MOE_MIGRATED_REVID=82725899

2 files changed, 93 insertions, 16 deletions

diff --git a/src/core/support/cpu_linux.c b/src/core/support/cpu_linux.c
new file mode 100644
index 0000000000..4d538a5b1b
--- /dev/null
+++ b/src/core/support/cpu_linux.c
@@ -0,0 +1,75 @@
+/*
+ *
+ * Copyright 2014, Google Inc.
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are
+ * met:
+ *
+ *     * Redistributions of source code must retain the above copyright
+ * notice, this list of conditions and the following disclaimer.
+ *     * Redistributions in binary form must reproduce the above
+ * copyright notice, this list of conditions and the following disclaimer
+ * in the documentation and/or other materials provided with the
+ * distribution.
+ *     * Neither the name of Google Inc. nor the names of its
+ * contributors may be used to endorse or promote products derived from
+ * this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+ * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+ * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+ * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+ * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+ * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+ * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ *
+ */
+
+#include <grpc/support/port_platform.h>
+
+#ifdef GPR_CPU_LINUX
+
+#include "src/core/support/cpu.h"
+
+#define _GNU_SOURCE
+#define __USE_GNU
+#define __USE_MISC
+#include <sched.h>
+#undef _GNU_SOURCE
+#undef __USE_GNU
+#undef __USE_MISC
+
+#include <errno.h>
+#include <unistd.h>
+#include <string.h>
+
+#include <grpc/support/log.h>
+
+int gpr_cpu_num_cores() {
+  static int ncpus = 0;
+  if (ncpus == 0) {
+    ncpus = sysconf(_SC_NPROCESSORS_ONLN);
+    if (ncpus < 1) {
+      gpr_log(GPR_ERROR, "Cannot determine number of CPUs: assuming 1");
+      ncpus = 1;
+    }
+  }
+  return ncpus;
+}
+
+int gpr_cpu_current_cpu() {
+  int cpu = sched_getcpu();
+  if (cpu < 0) {
+    gpr_log(GPR_ERROR, "Error determining current CPU: %s\n", strerror(errno));
+    return 0;
+  }
+  return cpu;
+}
+
+#endif /* GPR_CPU_LINUX */
diff --git a/src/core/support/cpu_posix.c b/src/core/support/cpu_posix.c
index 7f9cb8b4dd..3dd1c548b0 100644
--- a/src/core/support/cpu_posix.c
+++ b/src/core/support/cpu_posix.c
@@ -31,16 +31,11 @@
  *
  */
 
-#include "src/core/support/cpu.h"
+#include <grpc/support/port_platform.h>
+
+#ifdef GPR_CPU_POSIX
 
-#ifdef __linux__
-#define _GNU_SOURCE
-#define __USE_GNU
-#define __USE_MISC
-#include <sched.h>
-#undef _GNU_SOURCE
-#undef __USE_GNU
-#undef __USE_MISC
+#include "src/core/support/cpu.h"
 
 #include <errno.h>
 #include <unistd.h>
@@ -48,6 +43,8 @@
 
 #include <grpc/support/log.h>
 
+static __thread char magic_thread_local;
+
 int gpr_cpu_num_cores() {
   static int ncpus = 0;
   if (ncpus == 0) {
@@ -60,13 +57,18 @@ int gpr_cpu_num_cores() {
   return ncpus;
 }
 
+/* This is a cheap, but good enough, pointer hash for sharding things: */
+static size_t shard_ptr(const void *info) {
+  size_t x = (size_t)info;
+  return ((x >> 4) ^ (x >> 9) ^ (x >> 14)) % gpr_cpu_num_cores();
+}
+
 int gpr_cpu_current_cpu() {
-  int cpu = sched_getcpu();
-  if (cpu < 0) {
-    gpr_log(GPR_ERROR, "Error determining current CPU: %s\n", strerror(errno));
-    return 0;
-  }
-  return cpu;
+  /* NOTE: there's no way I know to return the actual cpu index portably...
+     most code that's using this is using it to shard across work queues though,
+     so here we use thread identity instead to achieve a similar though not
+     identical effect */
+  return shard_ptr(&magic_thread_local);
 }
 
-#endif /* __linux__ */
+#endif /* GPR_CPU_LINUX */