Add thread-specific caching for small size classes, based on magazines.

This caching allows for completely lock-free allocation/deallocation in the
steady state, at the expense of likely increased memory use and
fragmentation.

Reduce the default number of arenas to 2*ncpus, since thread-specific
caching typically reduces arena contention.

Modify size class spacing to include ranges of 2^n-spaced, quantum-spaced,
cacheline-spaced, and subpage-spaced size classes.  The advantages are:
fewer size classes, reduced false cacheline sharing, and reduced internal
fragmentation for allocations that are slightly over 512, 1024, etc.

Increase RUN_MAX_SMALL, in order to limit fragmentation for the
subpage-spaced size classes.

Add a size-->bin lookup table for small sizes to simplify translating sizes
to size classes.  Include a hard-coded constant table that is used unless
custom size class spacing is specified at run time.

Add the ability to disable tiny size classes at compile time via
MALLOC_TINY.

1 files changed, 6 insertions, 0 deletions

diff --git a/lib/libc/include/libc_private.h b/lib/libc/include/libc_private.h
index 70e1ef8..50903f3 100644
--- a/lib/libc/include/libc_private.h
+++ b/lib/libc/include/libc_private.h
@@ -158,6 +158,12 @@ void _set_tp(void *tp);
 extern const char *__progname;
 
 /*
+ * This function is used by the threading libraries to notify malloc that a
+ * thread is exiting.
+ */
+void _malloc_thread_cleanup(void);
+
+/*
  * These functions are used by the threading libraries in order to protect
  * malloc across fork().
  */