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[PATCH 2/5] Add single-threaded path to malloc/realloc/calloc/memalloc
- From: Wilco Dijkstra <Wilco dot Dijkstra at arm dot com>
- To: "libc-alpha at sourceware dot org" <libc-alpha at sourceware dot org>
- Cc: nd <nd at arm dot com>
- Date: Thu, 12 Oct 2017 09:35:26 +0000
- Subject: [PATCH 2/5] Add single-threaded path to malloc/realloc/calloc/memalloc
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This patch adds a single-threaded fast path to malloc, realloc,
calloc and memalloc. When we're single-threaded, we can bypass
arena_get (which always locks the arena it returns) and just use
the main arena. Also avoid retrying a different arena.
Passes GLIBC tests, OK for commit?
ChangeLog:
2017-10-11 Wilco Dijkstra <wdijkstr@arm.com>
* malloc/malloc.c (sysdep-cancel.h): Add include.
(__libc_malloc): Add SINGLE_THREAD_P path.
(__libc_realloc): Likewise.
(_mid_memalign): Likewise.
(__libc_calloc): Likewise.
--
diff --git a/malloc/malloc.c b/malloc/malloc.c
index 0dd095cb79e2bc2a4e111155bb9cb115e7f92d50..7db4816a358164822988e0e2752714a2643fdb26 100644
--- a/malloc/malloc.c
+++ b/malloc/malloc.c
@@ -243,6 +243,10 @@
#include <malloc/malloc-internal.h>
+/* For SINGLE_THREAD_P. */
+#include <sysdep-cancel.h>
+
+
/*
Debugging:
@@ -3034,6 +3038,14 @@ __libc_malloc (size_t bytes)
DIAG_POP_NEEDS_COMMENT;
#endif
+ if (SINGLE_THREAD_P)
+ {
+ victim = _int_malloc (&main_arena, bytes);
+ assert (!victim || chunk_is_mmapped (mem2chunk (victim)) ||
+ &main_arena == arena_for_chunk (mem2chunk (victim)));
+ return victim;
+ }
+
arena_get (ar_ptr, bytes);
victim = _int_malloc (ar_ptr, bytes);
@@ -3190,6 +3202,15 @@ __libc_realloc (void *oldmem, size_t bytes)
return newmem;
}
+ if (SINGLE_THREAD_P)
+ {
+ newp = _int_realloc (ar_ptr, oldp, oldsize, nb);
+ assert (!newp || chunk_is_mmapped (mem2chunk (newp)) ||
+ ar_ptr == arena_for_chunk (mem2chunk (newp)));
+
+ return newp;
+ }
+
__libc_lock_lock (ar_ptr->mutex);
newp = _int_realloc (ar_ptr, oldp, oldsize, nb);
@@ -3265,6 +3286,15 @@ _mid_memalign (size_t alignment, size_t bytes, void *address)
alignment = a;
}
+ if (SINGLE_THREAD_P)
+ {
+ p = _int_memalign (&main_arena, alignment, bytes);
+ assert (!p || chunk_is_mmapped (mem2chunk (p)) ||
+ &main_arena == arena_for_chunk (mem2chunk (p)));
+
+ return p;
+ }
+
arena_get (ar_ptr, bytes + alignment + MINSIZE);
p = _int_memalign (ar_ptr, alignment, bytes);
@@ -3357,7 +3387,11 @@ __libc_calloc (size_t n, size_t elem_size)
MAYBE_INIT_TCACHE ();
- arena_get (av, sz);
+ if (SINGLE_THREAD_P)
+ av = &main_arena;
+ else
+ arena_get (av, sz);
+
if (av)
{
/* Check if we hand out the top chunk, in which case there may be no
@@ -3387,19 +3421,21 @@ __libc_calloc (size_t n, size_t elem_size)
}
mem = _int_malloc (av, sz);
-
assert (!mem || chunk_is_mmapped (mem2chunk (mem)) ||
av == arena_for_chunk (mem2chunk (mem)));
- if (mem == 0 && av != NULL)
+ if (!SINGLE_THREAD_P)
{
- LIBC_PROBE (memory_calloc_retry, 1, sz);
- av = arena_get_retry (av, sz);
- mem = _int_malloc (av, sz);
- }
+ if (mem == 0 && av != NULL)
+ {
+ LIBC_PROBE (memory_calloc_retry, 1, sz);
+ av = arena_get_retry (av, sz);
+ mem = _int_malloc (av, sz);
+ }
- if (av != NULL)
- __libc_lock_unlock (av->mutex);
+ if (av != NULL)
+ __libc_lock_unlock (av->mutex);
+ }
/* Allocation failed even after a retry. */
if (mem == 0)