pjs/js/src/jsarena.c

/* -*- Mode: C; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 4 -*-
 *
 * The contents of this file are subject to the Netscape Public
 * License Version 1.1 (the "License"); you may not use this file
 * except in compliance with the License. You may obtain a copy of
 * the License at http://www.mozilla.org/NPL/
 *
 * Software distributed under the License is distributed on an "AS
 * IS" basis, WITHOUT WARRANTY OF ANY KIND, either express oqr
 * implied. See the License for the specific language governing
 * rights and limitations under the License.
 *
 * The Original Code is Mozilla Communicator client code, released
 * March 31, 1998.
 *
 * The Initial Developer of the Original Code is Netscape
 * Communications Corporation.  Portions created by Netscape are
 * Copyright (C) 1998 Netscape Communications Corporation. All
 * Rights Reserved.
 *
 * Contributor(s): 
 *
 * Alternatively, the contents of this file may be used under the
 * terms of the GNU Public License (the "GPL"), in which case the
 * provisions of the GPL are applicable instead of those above.
 * If you wish to allow use of your version of this file only
 * under the terms of the GPL and not to allow others to use your
 * version of this file under the NPL, indicate your decision by
 * deleting the provisions above and replace them with the notice
 * and other provisions required by the GPL.  If you do not delete
 * the provisions above, a recipient may use your version of this
 * file under either the NPL or the GPL.
 */

/*
 * Lifetime-based fast allocation, inspired by much prior art, including
 * "Fast Allocation and Deallocation of Memory Based on Object Lifetimes"
 * David R. Hanson, Software -- Practice and Experience, Vol. 20(1).
 */
#include "jsstddef.h"
#include <stdlib.h>
#include <string.h>
#include "jstypes.h"
#include "jsbit.h"
#include "jsarena.h" /* Added by JSIFY */
#include "jsutil.h" /* Added by JSIFY */

#ifdef JS_THREADSAFE
extern int js_CompareAndSwap(jsword *, jsword, jsword);
#endif

static JSArena *arena_freelist;

#ifdef JS_ARENAMETER
static JSArenaStats *arena_stats_list;

#define COUNT(pool,what)  (pool)->stats.what++
#else
#define COUNT(pool,what)  /* nothing */
#endif

#define JS_ARENA_DEFAULT_ALIGN  sizeof(double)

JS_EXPORT_API(void)
JS_InitArenaPool(JSArenaPool *pool, const char *name, JSUint32 size, JSUint32 align)
{
    if (align == 0)
	align = JS_ARENA_DEFAULT_ALIGN;
    pool->mask = JS_BITMASK(JS_CeilingLog2(align));
    pool->first.next = NULL;
    pool->first.base = pool->first.avail = pool->first.limit =
	(jsuword)JS_ARENA_ALIGN(pool, &pool->first + 1);
    pool->current = &pool->first;
    pool->arenasize = size;
#ifdef JS_ARENAMETER
    memset(&pool->stats, 0, sizeof pool->stats);
    pool->stats.name = strdup(name);
    pool->stats.next = arena_stats_list;
    arena_stats_list = &pool->stats;
#endif
}

JS_EXPORT_API(void *)
JS_ArenaAllocate(JSArenaPool *pool, JSUint32 nb)
{
    JSArena **ap, *a, *b;
#ifdef JS_THREADSAFE
    JSArena *c;
#endif
    JSUint32 sz;
    void *p;

    JS_ASSERT((nb & pool->mask) == 0);
#if defined(XP_PC) && !defined(_WIN32)
    if (nb >= 60000U)
	return 0;
#endif  /* WIN16 */
    ap = &arena_freelist;
    for (a = pool->current; a->avail + nb > a->limit; pool->current = a) {
        if (a->next) {                          /* move to next arena */
            a = a->next;
	    continue;
        }
	while ((b = *ap) != NULL) {		/* reclaim a free arena */
	    if (b->limit - b->base == pool->arenasize) {
#ifdef JS_THREADSAFE
		do {
                    b = *ap;
		    c = b->next;
		} while (!js_CompareAndSwap((jsword *)ap,(jsword)b,(jsword)c));
#else
		*ap = b->next;
#endif
		b->next = NULL;
		a = a->next = b;
		COUNT(pool, nreclaims);
		goto claim;
	    }
	    ap = &b->next;
	}
	sz = JS_MAX(pool->arenasize, nb);	/* allocate a new arena */
	sz += sizeof *a + pool->mask;           /* header and alignment slop */
	b = malloc(sz);
	if (!b)
	    return 0;
	a = a->next = b;
	a->next = NULL;
	a->limit = (jsuword)a + sz;
	JS_COUNT_ARENA(pool,++);
	COUNT(pool, nmallocs);
    claim:
	a->base = a->avail = (jsuword)JS_ARENA_ALIGN(pool, a + 1);
    }
    p = (void *)a->avail;
    a->avail += nb;
    return p;
}

JS_EXPORT_API(void *)
JS_ArenaGrow(JSArenaPool *pool, void *p, JSUint32 size, JSUint32 incr)
{
    void *newp;

    JS_ARENA_ALLOCATE(newp, pool, size + incr);
    memcpy(newp, p, size);
    return newp;
}

/*
 * Free tail arenas linked after head, which may not be the true list head.
 * Reset pool->current to point to head in case it pointed at a tail arena.
 */
static void
FreeArenaList(JSArenaPool *pool, JSArena *head, JSBool reallyFree)
{
    JSArena **ap, *a;
#ifdef JS_THREADSAFE
    JSArena *b;
#endif

    ap = &head->next;
    a = *ap;
    if (!a)
	return;

#ifdef DEBUG
    do {
	JS_ASSERT(a->base <= a->avail && a->avail <= a->limit);
	a->avail = a->base;
	JS_CLEAR_UNUSED(a);
    } while ((a = a->next) != NULL);
    a = *ap;
#endif

    if (reallyFree) {
	do {
	    *ap = a->next;
	    JS_CLEAR_ARENA(a);
	    JS_COUNT_ARENA(pool,--);
	    free(a);
	} while ((a = *ap) != NULL);
    } else {
	/* Insert the whole arena chain at the front of the freelist. */
	do {
	    ap = &(*ap)->next;
	} while (*ap);
#ifdef JS_THREADSAFE
	do {
	    *ap = b = arena_freelist;
	} while (!js_CompareAndSwap((jsword*)&arena_freelist,(jsword)b,(jsword)a));
#else
	*ap = arena_freelist;
	arena_freelist = a;
#endif
	head->next = NULL;
    }

    pool->current = head;
}

JS_EXPORT_API(void)
JS_ArenaRelease(JSArenaPool *pool, char *mark)
{
    JSArena *a;

    for (a = pool->first.next; a; a = a->next) {
	if (JS_UPTRDIFF(mark, a) < JS_UPTRDIFF(a->avail, a)) {
	    a->avail = (jsuword)JS_ARENA_ALIGN(pool, mark);
	    FreeArenaList(pool, a, JS_TRUE);
	    return;
	}
    }
}

JS_EXPORT_API(void)
JS_FreeArenaPool(JSArenaPool *pool)
{
    FreeArenaList(pool, &pool->first, JS_FALSE);
    COUNT(pool, ndeallocs);
}

JS_EXPORT_API(void)
JS_FinishArenaPool(JSArenaPool *pool)
{
    FreeArenaList(pool, &pool->first, JS_TRUE);
#ifdef JS_ARENAMETER
    {
	JSArenaStats *stats, **statsp;

	if (pool->stats.name)
	    free(pool->stats.name);
	for (statsp = &arena_stats_list; (stats = *statsp) != 0;
	     statsp = &stats->next) {
	    if (stats == &pool->stats) {
		*statsp = stats->next;
		return;
	    }
	}
    }
#endif
}

JS_EXPORT_API(void)
JS_CompactArenaPool(JSArenaPool *pool)
{
#if 0 /* XP_MAC */
    JSArena *a = pool->first.next;

    while (a) {
        reallocSmaller(a, a->avail - (jsuword)a);
        a->limit = a->avail;
        a = a->next;
    }
#endif
}

JS_EXPORT_API(void)
JS_ArenaFinish()
{
    JSArena *a, *next;

#ifdef JS_THREADSAFE
    while (arena_freelist) {
	a = arena_freelist;
	next = a->next;
	if (js_CompareAndSwap((jsword*)&arena_freelist,(jsword)a,(jsword)next))
	    free(a);
    }
#else
    for (a = arena_freelist; a; a = next) {
        next = a->next;
        free(a);
    }
    arena_freelist = NULL;
#endif
}

#ifdef JS_ARENAMETER
JS_EXPORT_API(void)
JS_ArenaCountAllocation(JSArenaPool *pool, JSUint32 nb)
{
    pool->stats.nallocs++;
    pool->stats.nbytes += nb;
    if (nb > pool->stats.maxalloc)
        pool->stats.maxalloc = nb;
    pool->stats.variance += nb * nb;
}

JS_EXPORT_API(void)
JS_ArenaCountInplaceGrowth(JSArenaPool *pool, JSUint32 size, JSUint32 incr)
{
    pool->stats.ninplace++;
}

JS_EXPORT_API(void)
JS_ArenaCountGrowth(JSArenaPool *pool, JSUint32 size, JSUint32 incr)
{
    pool->stats.ngrows++;
    pool->stats.nbytes += incr;
    pool->stats.variance -= size * size;
    size += incr;
    if (size > pool->stats.maxalloc)
        pool->stats.maxalloc = size;
    pool->stats.variance += size * size;
}

JS_EXPORT_API(void)
JS_ArenaCountRelease(JSArenaPool *pool, char *mark)
{
    pool->stats.nreleases++;
}

JS_EXPORT_API(void)
JS_ArenaCountRetract(JSArenaPool *pool, char *mark)
{
    pool->stats.nfastrels++;
}

#include <math.h>
#include <stdio.h>

JS_EXPORT_API(void)
JS_DumpArenaStats(FILE *fp)
{
    JSArenaStats *stats;
    double mean, variance;

    for (stats = arena_stats_list; stats; stats = stats->next) {
        if (stats->nallocs != 0) {
	    mean = (double)stats->nbytes / stats->nallocs;
	    variance = fabs(stats->variance / stats->nallocs - mean * mean);
	} else {
	    mean = variance = 0;
	}

        fprintf(fp, "\n%s allocation statistics:\n", stats->name);
        fprintf(fp, "              number of arenas: %u\n", stats->narenas);
        fprintf(fp, "         number of allocations: %u\n", stats->nallocs);
        fprintf(fp, " number of free arena reclaims: %u\n", stats->nreclaims);
        fprintf(fp, "        number of malloc calls: %u\n", stats->nmallocs);
        fprintf(fp, "       number of deallocations: %u\n", stats->ndeallocs);
        fprintf(fp, "  number of allocation growths: %u\n", stats->ngrows);
        fprintf(fp, "    number of in-place growths: %u\n", stats->ninplace);
        fprintf(fp, "number of released allocations: %u\n", stats->nreleases);
        fprintf(fp, "       number of fast releases: %u\n", stats->nfastrels);
        fprintf(fp, "         total bytes allocated: %u\n", stats->nbytes);
        fprintf(fp, "          mean allocation size: %g\n", mean);
        fprintf(fp, "            standard deviation: %g\n", sqrt(variance));
        fprintf(fp, "       maximum allocation size: %u\n", stats->maxalloc);
    }
}
#endif /* JS_ARENAMETER */