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Author: boulos
Date: Mon Feb 25 19:14:04 2008
New Revision: 2123

Modified:
   trunk/Core/Thread/Thread_pthreads.cc
   trunk/Engine/Control/RTRT.cc
Log:
Core/Thread/Thread_pthreads.cc

 Use sysctl to convert the user's requested cpu to an L2 cache group.

Engine/Control/RTRT.cc

 Use Thread::migrate to allow for people to use thread affinity when
 available (currently only on Apple Leopard, but we could add CMake
 checks for the NPTL and then use pthread_setaffinity_np if
 available).


Modified: trunk/Core/Thread/Thread_pthreads.cc
==============================================================================
--- trunk/Core/Thread/Thread_pthreads.cc        (original)
+++ trunk/Core/Thread/Thread_pthreads.cc        Mon Feb 25 19:14:04 2008
@@ -504,16 +504,30 @@
   }
 #ifdef APPLE_LEOPARD
   if (cpu_ != -1) {
+    // Using the Thread Affinity API
+    // 
(http://developer.apple.com/releasenotes/Performance/RN-AffinityAPI/index.html)
+    // we can tell the scheduler to try to put us on a shared L2
+    // cache. To convert the user's cpu_ number to an affinity tag, we
+    // first determine how many cores share an L2 cache and how many
+    // total cores there are. This information is gathered using
+    // sysctl.
     thread_affinity_policy ap;
-    // NOTE(boulos): To allow people to specify processors using
-    // 0-based indexing, we don't want them to end up with 0 meaning
-    // no affinity. OS X also can tell you how many "logical
-    // processors" share an L2 cache (which is all that the affinity
-    // scheduler priority "respects" anyway) so we might be able to
-    // just convert the cpu_ field here into an affinity tag. This
-    // would allow a linux implementation that had NPTL to use
-    // pthread_setaffinity_np directly on the actual core desired.
-    ap.affinity_tag = cpu_ + 1;
+    // hw.cacheconfig[0] is how many total logical processors there are 
(cores)
+    // hw.cacheconfig[1] is how many share an L1 (1 for now...)
+    // hw.cacheconfig[2] is how many share an L2 (2 on Clovertown)
+    int64_t cache_config[80];
+    size_t len = sizeof(cache_config);
+    if (sysctlbyname("hw.cacheconfig", cache_config, &len, NULL, 0) != 0) {
+      throw ThreadError("Unable to read hw.cacheconfig");
+    }
+    unsigned int num_cores = static_cast<unsigned int>(cache_config[0]);
+    unsigned int num_per_L2 = static_cast<unsigned int>(cache_config[2]);
+    unsigned int num_groups = num_cores / num_per_L2;
+    unsigned int cpu_group = cpu_ / num_per_L2;
+    cpu_group %= num_groups; // In case someone asks to overcommit the 
machine.
+
+    // The user wants this thread to be on cpu_, let's determine which
+    ap.affinity_tag = cpu_group + 1;
     thread_policy_set(pthread_mach_thread_np(priv_->threadid),
                       THREAD_AFFINITY_POLICY,
                       (integer_t*)&ap,

Modified: trunk/Engine/Control/RTRT.cc
==============================================================================
--- trunk/Engine/Control/RTRT.cc        (original)
+++ trunk/Engine/Control/RTRT.cc        Mon Feb 25 19:14:04 2008
@@ -513,16 +513,7 @@
       Thread* t = workers[i] =
         new Thread(new Worker(this, i, false), name.str().c_str(),
                    0, Thread::NotActivated);
-      // NOTE(boulos): It seems that the Mac OS X scheduler is
-      // actually much worse when you try to add priority. The docs
-      // claim that you should use affinity "groups" which basically
-      // means mapping thread ids to L2 caches. The i < 4 code should
-      // test this on 4-core processor systems. However, running
-      // bin/manta -np 8 on my 8-core mac pro, only 5 threads are
-      // running at peak.
-
-      //t->migrate((i < 4) ? 0 : 1);
-      //t->migrate(i);
+      t->migrate(i);
       t->setStackSize(RENDER_THREAD_STACKSIZE);
       t->activate(false);
     }
@@ -807,6 +798,7 @@
           workers[i] = new Thread(new Worker(this, i, true), 
name.str().c_str(),
                                   0, Thread::NotActivated);
 
+          workers[i]->migrate(i);
           // Set the stack size.
           workers[i]->setStackSize(RENDER_THREAD_STACKSIZE);
 

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• [Manta] r2123 - in trunk: Core/Thread Engine/Control, Solomon Boulos, 02/25/2008
  • Re: [Manta] r2123 - in trunk: Core/Thread Engine/Control, Solomon Boulos, 02/25/2008

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