The Tor Browser: nsprpub/lib/ds/plarena.c@b8a032363ba2 (annotated)

nsprpub/lib/ds/plarena.c@b8a032363ba2 (annotated)

nsprpub/lib/ds/plarena.c

Thu, 22 Jan 2015 13:21:57 +0100

author: Michael Schloh von Bennewitz <michael@schloh.com>
date: Thu, 22 Jan 2015 13:21:57 +0100
branch: TOR_BUG_9701
changeset 15: b8a032363ba2
permissions: -rw-r--r--

Incorporate requested changes from Mozilla in review:
https://bugzilla.mozilla.org/show_bug.cgi?id=1123480#c6

 /* -*- Mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
 /* This Source Code Form is subject to the terms of the Mozilla Public
  * License, v. 2.0. If a copy of the MPL was not distributed with this
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
 /*
  * 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 <stdlib.h>
 #include <string.h>
 #include "plarena.h"
 #include "prmem.h"
 #include "prbit.h"
 #include "prlog.h"
 #include "prlock.h"
 #include "prinit.h"
 static PLArena *arena_freelist;
 #ifdef PL_ARENAMETER
 static PLArenaStats *arena_stats_list;
 #define COUNT(pool,what)  (pool)->stats.what++
 #else
 #define COUNT(pool,what)  /* nothing */
 #endif
 #define PL_ARENA_DEFAULT_ALIGN  sizeof(double)
 static PRLock    *arenaLock;
 static PRCallOnceType once;
 static const PRCallOnceType pristineCallOnce;
 /*
 ** InitializeArenas() -- Initialize arena operations.
 **
 ** InitializeArenas() is called exactly once and only once from
 ** LockArena(). This function creates the arena protection
 ** lock: arenaLock.
 **
 ** Note: If the arenaLock cannot be created, InitializeArenas()
 ** fails quietly, returning only PR_FAILURE. This percolates up
 ** to the application using the Arena API. He gets no arena
 ** from PL_ArenaAllocate(). It's up to him to fail gracefully
 ** or recover.
 **
 */
 static PRStatus InitializeArenas( void )
 {
     PR_ASSERT( arenaLock == NULL );
     arenaLock = PR_NewLock();
     if ( arenaLock == NULL )
         return PR_FAILURE;
     else
         return PR_SUCCESS;
 } /* end ArenaInitialize() */
 static PRStatus LockArena( void )
 {
     PRStatus rc = PR_CallOnce( &once, InitializeArenas );
     if ( PR_FAILURE != rc )
         PR_Lock( arenaLock );
     return(rc);
 } /* end LockArena() */
 static void UnlockArena( void )
 {
     PR_Unlock( arenaLock );
     return;
 } /* end UnlockArena() */
 PR_IMPLEMENT(void) PL_InitArenaPool(
     PLArenaPool *pool, const char *name, PRUint32 size, PRUint32 align)
 {
     /*
      * Look-up table of PR_BITMASK(PR_CeilingLog2(align)) values for
      * align = 1 to 32.
      */
     static const PRUint8 pmasks[33] = {
 ,                                               /*  not used */
 , 1, 3, 3, 7, 7, 7, 7,15,15,15,15,15,15,15,15,  /*  1 ... 16 */
 ,31,31,31,31,31,31,31,31,31,31,31,31,31,31,31}; /* 17 ... 32 */
     if (align == 0)
         align = PL_ARENA_DEFAULT_ALIGN;
     if (align < sizeof(pmasks)/sizeof(pmasks[0]))
         pool->mask = pmasks[align];
     else
         pool->mask = PR_BITMASK(PR_CeilingLog2(align));
     pool->first.next = NULL;
     pool->first.base = pool->first.avail = pool->first.limit =
         (PRUword)PL_ARENA_ALIGN(pool, &pool->first + 1);
     pool->current = &pool->first;
     /*
      * Compute the net size so that each arena's gross size is |size|.
      * sizeof(PLArena) + pool->mask is the header and alignment slop
      * that PL_ArenaAllocate adds to the net size.
      */
     if (size > sizeof(PLArena) + pool->mask)
         pool->arenasize = size - (sizeof(PLArena) + pool->mask);
     else
         pool->arenasize = size;
 #ifdef PL_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
 }
 /*
 ** PL_ArenaAllocate() -- allocate space from an arena pool
 **
 ** Description: PL_ArenaAllocate() allocates space from an arena
 ** pool.
 **
 ** First, try to satisfy the request from arenas starting at
 ** pool->current.
 **
 ** If there is not enough space in the arena pool->current, try
 ** to claim an arena, on a first fit basis, from the global
 ** freelist (arena_freelist).
 **
 ** If no arena in arena_freelist is suitable, then try to
 ** allocate a new arena from the heap.
 **
 ** Returns: pointer to allocated space or NULL
 **
 ** Notes: The original implementation had some difficult to
 ** solve bugs; the code was difficult to read. Sometimes it's
 ** just easier to rewrite it. I did that. larryh.
 **
 ** See also: bugzilla: 45343.
 **
 */
 PR_IMPLEMENT(void *) PL_ArenaAllocate(PLArenaPool *pool, PRUint32 nb)
 {
     PLArena *a;
     char *rp;     /* returned pointer */
     PR_ASSERT((nb & pool->mask) == 0);
     nb = (PRUword)PL_ARENA_ALIGN(pool, nb); /* force alignment */
     /* attempt to allocate from arenas at pool->current */
     {
         a = pool->current;
         do {
             if ( nb <= a->limit - a->avail )  {
                 pool->current = a;
                 rp = (char *)a->avail;
                 a->avail += nb;
                 return rp;
             }
         } while( NULL != (a = a->next) );
     }
     /* attempt to allocate from arena_freelist */
     {
         PLArena *p; /* previous pointer, for unlinking from freelist */
         /* lock the arena_freelist. Make access to the freelist MT-Safe */
         if ( PR_FAILURE == LockArena())
             return(0);
         for ( a = arena_freelist, p = NULL; a != NULL ; p = a, a = a->next ) {
             if ( nb <= a->limit - a->base )  {
                 if ( p == NULL )
                     arena_freelist = a->next;
                 else
                     p->next = a->next;
                 UnlockArena();
                 a->avail = a->base;
                 rp = (char *)a->avail;
                 a->avail += nb;
                 /* the newly allocated arena is linked after pool->current
                 *  and becomes pool->current */
                 a->next = pool->current->next;
                 pool->current->next = a;
                 pool->current = a;
                 if ( NULL == pool->first.next )
                     pool->first.next = a;
                 return(rp);
             }
         }
         UnlockArena();
     }
     /* attempt to allocate from the heap */
     {
         PRUint32 sz = PR_MAX(pool->arenasize, nb);
         if (PR_UINT32_MAX - sz < sizeof *a + pool->mask) {
             a = NULL;
         } else {
             sz += sizeof *a + pool->mask;  /* header and alignment slop */
             a = (PLArena*)PR_MALLOC(sz);
         }
         if ( NULL != a )  {
             a->limit = (PRUword)a + sz;
             a->base = a->avail = (PRUword)PL_ARENA_ALIGN(pool, a + 1);
             PL_MAKE_MEM_NOACCESS((void*)a->avail, a->limit - a->avail);
             rp = (char *)a->avail;
             a->avail += nb;
             /* the newly allocated arena is linked after pool->current
             *  and becomes pool->current */
             a->next = pool->current->next;
             pool->current->next = a;
             pool->current = a;
             if ( NULL == pool->first.next )
                 pool->first.next = a;
             PL_COUNT_ARENA(pool,++);
             COUNT(pool, nmallocs);
             return(rp);
         }
     }
     /* we got to here, and there's no memory to allocate */
     return(NULL);
 } /* --- end PL_ArenaAllocate() --- */
 PR_IMPLEMENT(void *) PL_ArenaGrow(
     PLArenaPool *pool, void *p, PRUint32 size, PRUint32 incr)
 {
     void *newp;
     PL_ARENA_ALLOCATE(newp, pool, size + incr);
     if (newp)
         memcpy(newp, p, size);
     return newp;
 }
 static void ClearArenaList(PLArena *a, PRInt32 pattern)
 {
     for (; a; a = a->next) {
         PR_ASSERT(a->base <= a->avail && a->avail <= a->limit);
         a->avail = a->base;
         PL_CLEAR_UNUSED_PATTERN(a, pattern);
         PL_MAKE_MEM_NOACCESS((void*)a->avail, a->limit - a->avail);
     }
 }
 PR_IMPLEMENT(void) PL_ClearArenaPool(PLArenaPool *pool, PRInt32 pattern)
 {
     ClearArenaList(pool->first.next, pattern);
 }
 /*
  * 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(PLArenaPool *pool, PLArena *head, PRBool reallyFree)
 {
     PLArena **ap, *a;
     ap = &head->next;
     a = *ap;
     if (!a)
         return;
 #ifdef DEBUG
     ClearArenaList(a, PL_FREE_PATTERN);
 #endif
     if (reallyFree) {
         do {
             *ap = a->next;
             PL_CLEAR_ARENA(a);
             PL_COUNT_ARENA(pool,--);
             PR_DELETE(a);
         } while ((a = *ap) != 0);
     } else {
         /* Insert the whole arena chain at the front of the freelist. */
         do {
             PL_MAKE_MEM_NOACCESS((void*)(*ap)->base,
                                  (*ap)->limit - (*ap)->base);
             ap = &(*ap)->next;
         } while (*ap);
         LockArena();
         *ap = arena_freelist;
         arena_freelist = a;
         head->next = 0;
         UnlockArena();
     }
     pool->current = head;
 }
 PR_IMPLEMENT(void) PL_ArenaRelease(PLArenaPool *pool, char *mark)
 {
     PLArena *a;
     for (a = &pool->first; a; a = a->next) {
         if (PR_UPTRDIFF(mark, a->base) <= PR_UPTRDIFF(a->avail, a->base)) {
             a->avail = (PRUword)PL_ARENA_ALIGN(pool, mark);
             FreeArenaList(pool, a, PR_FALSE);
             return;
         }
     }
 }
 PR_IMPLEMENT(void) PL_FreeArenaPool(PLArenaPool *pool)
 {
     FreeArenaList(pool, &pool->first, PR_FALSE);
     COUNT(pool, ndeallocs);
 }
 PR_IMPLEMENT(void) PL_FinishArenaPool(PLArenaPool *pool)
 {
     FreeArenaList(pool, &pool->first, PR_TRUE);
 #ifdef PL_ARENAMETER
     {
         PLArenaStats *stats, **statsp;
         if (pool->stats.name)
             PR_DELETE(pool->stats.name);
         for (statsp = &arena_stats_list; (stats = *statsp) != 0;
              statsp = &stats->next) {
             if (stats == &pool->stats) {
                 *statsp = stats->next;
                 return;
             }
         }
     }
 #endif
 }
 PR_IMPLEMENT(void) PL_CompactArenaPool(PLArenaPool *ap)
 {
 }
 PR_IMPLEMENT(void) PL_ArenaFinish(void)
 {
     PLArena *a, *next;
     for (a = arena_freelist; a; a = next) {
         next = a->next;
         PR_DELETE(a);
     }
     arena_freelist = NULL;
     if (arenaLock) {
         PR_DestroyLock(arenaLock);
         arenaLock = NULL;
     }
     once = pristineCallOnce;
 }
 PR_IMPLEMENT(size_t) PL_SizeOfArenaPoolExcludingPool(
     const PLArenaPool *pool, PLMallocSizeFn mallocSizeOf)
 {
     /*
      * The first PLArena is within |pool|, so don't measure it.  Subsequent
      * PLArenas are separate and must be measured.
      */
     size_t size = 0;
     const PLArena *arena = pool->first.next;
     while (arena) {
         size += mallocSizeOf(arena);
         arena = arena->next;
     }
     return size;
 }
 #ifdef PL_ARENAMETER
 PR_IMPLEMENT(void) PL_ArenaCountAllocation(PLArenaPool *pool, PRUint32 nb)
 {
     pool->stats.nallocs++;
     pool->stats.nbytes += nb;
     if (nb > pool->stats.maxalloc)
         pool->stats.maxalloc = nb;
     pool->stats.variance += nb * nb;
 }
 PR_IMPLEMENT(void) PL_ArenaCountInplaceGrowth(
     PLArenaPool *pool, PRUint32 size, PRUint32 incr)
 {
     pool->stats.ninplace++;
 }
 PR_IMPLEMENT(void) PL_ArenaCountGrowth(
     PLArenaPool *pool, PRUint32 size, PRUint32 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;
 }
 PR_IMPLEMENT(void) PL_ArenaCountRelease(PLArenaPool *pool, char *mark)
 {
     pool->stats.nreleases++;
 }
 PR_IMPLEMENT(void) PL_ArenaCountRetract(PLArenaPool *pool, char *mark)
 {
     pool->stats.nfastrels++;
 }
 #include <math.h>
 #include <stdio.h>
 PR_IMPLEMENT(void) PL_DumpArenaStats(FILE *fp)
 {
     PLArenaStats *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 /* PL_ARENAMETER */

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nsprpub/lib/ds/plarena.c@b8a032363ba2 (annotated)

nsprpub/lib/ds/plarena.c