Make malloc() go 200x faster

If pthread_create() is linked into the binary, then the cosmo runtime
will create an independent dlmalloc arena for each core. Whenever the
malloc() function is used it will index `g_heaps[sched_getcpu() / 2]`
to find the arena with the greatest hyperthread / numa locality. This
may be configured via an environment variable. For example if you say
`export COSMOPOLITAN_HEAP_COUNT=1` then you can restore the old ways.
Your process may be configured to have anywhere between 1 - 128 heaps

We need this revision because it makes multithreaded C++ applications
faster. For example, an HTTP server I'm working on that makes extreme
use of the STL went from 16k to 2000k requests per second, after this
change was made. To understand why, try out the malloc_test benchmark
which calls malloc() + realloc() in a loop across many threads, which
sees a a 250x improvement in process clock time and 200x on wall time

The tradeoff is this adds ~25ns of latency to individual malloc calls
compared to MODE=tiny, once the cosmo runtime has transitioned into a
fully multi-threaded state. If you don't need malloc() to be scalable
then cosmo provides many options for you. For starters the heap count
variable above can be set to put the process back in single heap mode
plus you can go even faster still, if you include tinymalloc.inc like
many of the programs in tool/build/.. are already doing since that'll
shave tens of kb off your binary footprint too. Theres also MODE=tiny
which is configured to use just 1 plain old dlmalloc arena by default

Another tradeoff is we need more memory now (except in MODE=tiny), to
track the provenance of memory allocation. This is so allocations can
be freely shared across threads, and because OSes can reschedule code
to different CPUs at any time.

third_party/dlmalloc/dlmalloc.h

@@ -25,6 +25,28 @@
 #define dlrealloc_in_place           __dlrealloc_in_place
 #define dlrealloc_in_place           __dlrealloc_in_place
 
+#define create_mspace_with_base      __create_mspace_with_base
+#define mspace_bulk_free             __mspace_bulk_free
+#define mspace_calloc                __mspace_calloc
+#define mspace_footprint             __mspace_footprint
+#define mspace_footprint_limit       __mspace_footprint_limit
+#define mspace_free                  __mspace_free
+#define mspace_independent_calloc    __mspace_independent_calloc
+#define mspace_independent_comalloc  __mspace_independent_comalloc
+#define mspace_inspect_all           __mspace_inspect_all
+#define mspace_mallinfo              __mspace_mallinfo
+#define mspace_malloc                __mspace_malloc
+#define mspace_malloc_stats          __mspace_malloc_stats
+#define mspace_mallopt               __mspace_mallopt
+#define mspace_max_footprint         __mspace_max_footprint
+#define mspace_memalign              __mspace_memalign
+#define mspace_realloc               __mspace_realloc
+#define mspace_realloc_in_place      __mspace_realloc_in_place
+#define mspace_set_footprint_limit   __mspace_set_footprint_limit
+#define mspace_track_large_chunks    __mspace_track_large_chunks
+#define mspace_trim                  __mspace_trim
+#define mspace_usable_size           __mspace_usable_size
+
 COSMOPOLITAN_C_START_
 
 /*
@@ -41,7 +63,7 @@ COSMOPOLITAN_C_START_
   maximum supported value of n differs across systems, but is in all
   cases less than the maximum representable value of a size_t.
 */
-void* dlmalloc(size_t);
+extern void* (*dlmalloc)(size_t);
 
 /*
   free(void* p)
@@ -57,7 +79,7 @@ void dlfree(void*);
   Returns a pointer to n_elements * element_size bytes, with all locations
   set to zero.
 */
-void* dlcalloc(size_t, size_t);
+extern void* (*dlcalloc)(size_t, size_t);
 
 /*
   realloc(void* p, size_t n)
@@ -81,7 +103,7 @@ void* dlcalloc(size_t, size_t);
   The old unix realloc convention of allowing the last-free'd chunk
   to be used as an argument to realloc is not supported.
 */
-void* dlrealloc(void*, size_t);
+extern void* (*dlrealloc)(void*, size_t);
 
 /*
   realloc_in_place(void* p, size_t n)
@@ -110,7 +132,7 @@ void* dlrealloc_in_place(void*, size_t);
 
   Overreliance on memalign is a sure way to fragment space.
 */
-void* dlmemalign(size_t, size_t);
+extern void* (*dlmemalign)(size_t, size_t);
 
 /*
   mallopt(int parameter_number, int parameter_value)
@@ -233,7 +255,7 @@ void dlmalloc_inspect_all(void (*handler)(void*, void*, size_t, void*),
   thus be inaccurate.
 */
 
-struct mallinfo dlmallinfo(void);
+extern struct mallinfo (*dlmallinfo)(void);
 
 /*
   independent_calloc(size_t n_elements, size_t element_size, void* chunks[]);