Merge tcmalloc r111 (perftools v. 1.8) with the chromium/ branch.

third_party/tcmalloc/chromium/src/common.h

Index: third_party/tcmalloc/chromium/src/common.h
===================================================================
--- third_party/tcmalloc/chromium/src/common.h	(revision 94429)
+++ third_party/tcmalloc/chromium/src/common.h	(working copy)
@@ -63,16 +63,15 @@
 
 #if defined(TCMALLOC_LARGE_PAGES)
 static const size_t kPageShift  = 15;
-static const size_t kNumClasses = 95;
-static const size_t kMaxThreadCacheSize = 4 << 20;
+static const size_t kNumClasses = 78;
 #else
-static const size_t kPageShift  = 12;
-static const size_t kNumClasses = 61;
-static const size_t kMaxThreadCacheSize = 2 << 20;
+static const size_t kPageShift  = 13;

[jar (doing other things), 2011/07/31 08:19:39]

This is the change to 8K pages from 4K.  The recent paper suggests this works
well for servers, but we really need to tune this for Chrome (or at least watch
that we don't see a regression when we land this).

+static const size_t kNumClasses = 86;
 #endif
+static const size_t kMaxThreadCacheSize = 4 << 20;

[jar (doing other things), 2011/07/31 08:19:39]

This looks like another change (for us, since we don't use LARGE_PAGES).  I
don't recall seeing a justification for this tuning change.

 
 static const size_t kPageSize   = 1 << kPageShift;
-static const size_t kMaxSize    = 8u * kPageSize;
+static const size_t kMaxSize    = 256 * 1024;

[jar (doing other things), 2011/07/31 08:19:39]

This is a big tuning change, upping the cutoff point to 256K from 32K.
Although we allocate IO buffers of 32K size, I don't think we do much larger
allocating.  Also, the 32K allocations will now be carved, and might not be
coalesced to spans and returned to the OS... which would notably raise our
committed memory footprint.

This tuning change is especially unclear for us on Chrome (unless I'm
mis-remembering the algorithms and mis-guessing the impact)

 static const size_t kAlignment  = 8;
 // For all span-lengths < kMaxPages we keep an exact-size list.
 static const size_t kMaxPages = 1 << (20 - kPageShift);
@@ -165,7 +164,7 @@
   //   32768      (32768 + 127 + (120<<7)) / 128  376
   static const int kMaxSmallSize = 1024;
   static const size_t kClassArraySize =
-      (((1 << kPageShift) * 8u + 127 + (120 << 7)) >> 7) + 1;
+      ((kMaxSize + 127 + (120 << 7)) >> 7) + 1;
   unsigned char class_array_[kClassArraySize];
 
   // Compute index of the class_array[] entry for a given size