Module Name: src
Committed By: njoly
Date: Sat Feb 26 23:27:49 UTC 2011
Modified Files:
src/lib/libc/stdlib: jemalloc.c
Log Message:
Switch from floating point to fixed point integer for run sizes maths.
>From FreeBSD (part of revision 1.154).
To generate a diff of this commit:
cvs rdiff -u -r1.21 -r1.22 src/lib/libc/stdlib/jemalloc.c
Please note that diffs are not public domain; they are subject to the
copyright notices on the relevant files.
Modified files:
Index: src/lib/libc/stdlib/jemalloc.c
diff -u src/lib/libc/stdlib/jemalloc.c:1.21 src/lib/libc/stdlib/jemalloc.c:1.22
--- src/lib/libc/stdlib/jemalloc.c:1.21 Thu Mar 4 22:48:31 2010
+++ src/lib/libc/stdlib/jemalloc.c Sat Feb 26 23:27:49 2011
@@ -1,4 +1,4 @@
-/* $NetBSD: jemalloc.c,v 1.21 2010/03/04 22:48:31 enami Exp $ */
+/* $NetBSD: jemalloc.c,v 1.22 2011/02/26 23:27:49 njoly Exp $ */
/*-
* Copyright (C) 2006,2007 Jason Evans <jas...@freebsd.org>.
@@ -118,7 +118,7 @@
#include <sys/cdefs.h>
/* __FBSDID("$FreeBSD: src/lib/libc/stdlib/malloc.c,v 1.147 2007/06/15 22:00:16 jasone Exp $"); */
-__RCSID("$NetBSD: jemalloc.c,v 1.21 2010/03/04 22:48:31 enami Exp $");
+__RCSID("$NetBSD: jemalloc.c,v 1.22 2011/02/26 23:27:49 njoly Exp $");
#ifdef __FreeBSD__
#include "libc_private.h"
@@ -319,20 +319,25 @@
#define SMALL_MAX_DEFAULT (1 << SMALL_MAX_2POW_DEFAULT)
/*
- * Maximum desired run header overhead. Runs are sized as small as possible
- * such that this setting is still honored, without violating other constraints.
- * The goal is to make runs as small as possible without exceeding a per run
- * external fragmentation threshold.
+ * RUN_MAX_OVRHD indicates maximum desired run header overhead. Runs are sized
+ * as small as possible such that this setting is still honored, without
+ * violating other constraints. The goal is to make runs as small as possible
+ * without exceeding a per run external fragmentation threshold.
*
- * Note that it is possible to set this low enough that it cannot be honored
- * for some/all object sizes, since there is one bit of header overhead per
- * object (plus a constant). In such cases, this constraint is relaxed.
+ * We use binary fixed point math for overhead computations, where the binary
+ * point is implicitly RUN_BFP bits to the left.
*
- * RUN_MAX_OVRHD_RELAX specifies the maximum number of bits per region of
- * overhead for which RUN_MAX_OVRHD is relaxed.
+ * Note that it is possible to set RUN_MAX_OVRHD low enough that it cannot be
+ * honored for some/all object sizes, since there is one bit of header overhead
+ * per object (plus a constant). This constraint is relaxed (ignored) for runs
+ * that are so small that the per-region overhead is greater than:
+ *
+ * (RUN_MAX_OVRHD / (reg_size << (3+RUN_BFP))
*/
-#define RUN_MAX_OVRHD 0.015
-#define RUN_MAX_OVRHD_RELAX 1.5
+#define RUN_BFP 12
+/* \/ Implicit binary fixed point. */
+#define RUN_MAX_OVRHD 0x0000003dU
+#define RUN_MAX_OVRHD_RELAX 0x00001800U
/* Put a cap on small object run size. This overrides RUN_MAX_OVRHD. */
#define RUN_MAX_SMALL_2POW 15
@@ -2143,7 +2148,6 @@
size_t try_run_size, good_run_size;
unsigned good_nregs, good_mask_nelms, good_reg0_offset;
unsigned try_nregs, try_mask_nelms, try_reg0_offset;
- float max_ovrhd = RUN_MAX_OVRHD;
assert(min_run_size >= pagesize);
assert(min_run_size <= arena_maxclass);
@@ -2161,7 +2165,7 @@
*/
try_run_size = min_run_size;
try_nregs = (unsigned)(((try_run_size - sizeof(arena_run_t)) /
- bin->reg_size) + 1); /* Counter-act the first line of the loop. */
+ bin->reg_size) + 1); /* Counter-act try_nregs-- in loop. */
do {
try_nregs--;
try_mask_nelms = (try_nregs >> (SIZEOF_INT_2POW + 3)) +
@@ -2195,9 +2199,8 @@
} while (sizeof(arena_run_t) + (sizeof(unsigned) *
(try_mask_nelms - 1)) > try_reg0_offset);
} while (try_run_size <= arena_maxclass && try_run_size <= RUN_MAX_SMALL
- && max_ovrhd > RUN_MAX_OVRHD_RELAX / ((float)(bin->reg_size << 3))
- && ((float)(try_reg0_offset)) / ((float)(try_run_size)) >
- max_ovrhd);
+ && RUN_MAX_OVRHD * (bin->reg_size << 3) > RUN_MAX_OVRHD_RELAX
+ && (try_reg0_offset << RUN_BFP) > RUN_MAX_OVRHD * try_run_size);
assert(sizeof(arena_run_t) + (sizeof(unsigned) * (good_mask_nelms - 1))
<= good_reg0_offset);
