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Switch from floating point to fixed point integer for run sizes maths. 

From FreeBSD (part of revision 1.154).
This commit is contained in:
njoly 2011-02-26 23:27:49 +00:00
parent 78733349d6
commit 51cca89d16
1 changed files with 21 additions and 18 deletions
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39
lib/libc/stdlib/jemalloc.c
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@ -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 <jasone@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 @@ __strerror_r(int e, char *s, size_t l)
#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 @@ arena_bin_run_size_calc(arena_bin_t *bin, size_t min_run_size)
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 @@ arena_bin_run_size_calc(arena_bin_t *bin, size_t min_run_size)
*/
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 @@ arena_bin_run_size_calc(arena_bin_t *bin, size_t min_run_size)
} 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);