Let the OS clear large new objects

Prefer calloc to malloc+memset when allocating large zeroed objects.
This avoids page thrashing when (make-vector 1000000000 nil)
allocates a large nil vector, as Emacs need not touch the
vector’s pages.  This wins on platforms like GNU/Linux where
calloc can fiddle with page tables to create a block of memory
that is lazily zeroed.
* src/alloc.c (lisp_malloc, lmalloc, allocate_vectorlike):
New arg CLEARIT to tell callee whether to use malloc or calloc.
All callers changed.
(allocate_clear_vector, allocate_nil_vector): New functions.
* src/alloc.c (xzalloc, make_vector):
* src/lisp.h (make_nil_vector):
Prefer calloc to malloc + memset(...,0,...).

1 files changed, 2 insertions, 3 deletions

diff --git a/src/lisp.h b/src/lisp.h
index 8674fe11a64..356692d53a1 100644
--- a/src/lisp.h
+++ b/src/lisp.h
@@ -3942,6 +3942,7 @@ extern Lisp_Object pure_cons (Lisp_Object, Lisp_Object);
 extern Lisp_Object make_vector (ptrdiff_t, Lisp_Object);
 extern void make_byte_code (struct Lisp_Vector *);
 extern struct Lisp_Vector *allocate_vector (ptrdiff_t);
+extern struct Lisp_Vector *allocate_nil_vector (ptrdiff_t);
 
 /* Make an uninitialized vector for SIZE objects.  NOTE: you must
    be sure that GC cannot happen until the vector is completely
@@ -3977,9 +3978,7 @@ make_uninit_sub_char_table (int depth, int min_char)
 INLINE Lisp_Object
 make_nil_vector (ptrdiff_t size)
 {
-  Lisp_Object vec = make_uninit_vector (size);
-  memclear (XVECTOR (vec)->contents, size * word_size);
-  return vec;
+  return make_lisp_ptr (allocate_nil_vector (size), Lisp_Vectorlike);
 }
 
 extern struct Lisp_Vector *allocate_pseudovector (int, int, int,