change to having four freelists per size, to reduce another source of

deterministic behavior. four selected because it's more than three, less
than five. i.e., no particular reason.

diff --git a/lib/libc/stdlib/malloc.c b/lib/libc/stdlib/malloc.c
index 361294e..c0542fc 100644 (file)
--- a/lib/libc/stdlib/malloc.c
+++ b/lib/libc/stdlib/malloc.c
@@ -1,4 +1,4 @@
-/*     $OpenBSD: malloc.c,v 1.162 2014/05/10 18:14:55 otto Exp $       */
+/*     $OpenBSD: malloc.c,v 1.163 2014/05/12 19:02:20 tedu Exp $       */
 /*
  * Copyright (c) 2008, 2010, 2011 Otto Moerbeek <otto@drijf.net>
  * Copyright (c) 2012 Matthew Dempsky <matthew@openbsd.org>
@@ -64,6 +64,7 @@
 #define MALLOC_DELAYED_CHUNK_MASK      15
 #define MALLOC_INITIAL_REGIONS 512
 #define MALLOC_DEFAULT_CACHE   64
+#define        MALLOC_CHUNK_LISTS      4
 
 /*
  * When the P option is active, we move allocations between half a page
@@ -110,7 +111,7 @@ struct dir_info {
                                        /* lists of free chunk info structs */
        struct chunk_head chunk_info_list[MALLOC_MAXSHIFT + 1];
                                        /* lists of chunks with free slots */
-       struct chunk_head chunk_dir[MALLOC_MAXSHIFT + 1];
+       struct chunk_head chunk_dir[MALLOC_MAXSHIFT + 1][MALLOC_CHUNK_LISTS];
        size_t free_regions_size;       /* free pages cached */
                                        /* free pages cache */
        struct region_info free_regions[MALLOC_MAXCACHE];
@@ -621,7 +622,8 @@ omalloc_init(struct dir_info **dp)
        }
        for (i = 0; i <= MALLOC_MAXSHIFT; i++) {
                LIST_INIT(&d->chunk_info_list[i]);
-               LIST_INIT(&d->chunk_dir[i]);
+               for (j = 0; j < MALLOC_CHUNK_LISTS; j++)
+                       LIST_INIT(&d->chunk_dir[i][j]);
        }
        malloc_used += regioninfo_size;
        d->canary1 = mopts.malloc_canary ^ (u_int32_t)(uintptr_t)d;
@@ -816,7 +818,7 @@ delete(struct dir_info *d, struct region_info *ri)
  * Allocate a page of chunks
  */
 static struct chunk_info *
-omalloc_make_chunks(struct dir_info *d, int bits)
+omalloc_make_chunks(struct dir_info *d, int bits, int listnum)
 {
        struct chunk_info *bp;
        void            *pp;
@@ -867,7 +869,7 @@ omalloc_make_chunks(struct dir_info *d, int bits)
        for (; i < k; i++)
                bp->bits[i / MALLOC_BITS] |= (u_short)1U << (i % MALLOC_BITS);
 
-       LIST_INSERT_HEAD(&d->chunk_dir[bits], bp, entries);
+       LIST_INSERT_HEAD(&d->chunk_dir[bits][listnum], bp, entries);
 
        bits++;
        if ((uintptr_t)pp & bits)
@@ -884,7 +886,7 @@ omalloc_make_chunks(struct dir_info *d, int bits)
 static void *
 malloc_bytes(struct dir_info *d, size_t size, void *f)
 {
-       int             i, j;
+       int             i, j, listnum;
        size_t          k;
        u_short         u, *lp;
        struct chunk_info *bp;
@@ -907,13 +909,13 @@ malloc_bytes(struct dir_info *d, size_t size, void *f)
                        j++;
        }
 
+       listnum = getrbyte() % MALLOC_CHUNK_LISTS;
        /* If it's empty, make a page more of that size chunks */
-       if (LIST_EMPTY(&d->chunk_dir[j])) {
-               bp = omalloc_make_chunks(d, j);
+       if ((bp = LIST_FIRST(&d->chunk_dir[j][listnum])) == NULL) {
+               bp = omalloc_make_chunks(d, j, listnum);
                if (bp == NULL)
                        return NULL;
-       } else
-               bp = LIST_FIRST(&d->chunk_dir[j]);
+       }
 
        if (bp->canary != d->canary1)
                wrterror("chunk info corrupted", NULL);
@@ -973,7 +975,7 @@ free_bytes(struct dir_info *d, struct region_info *r, void *ptr)
 {
        struct chunk_head *mp;
        struct chunk_info *info;
-       int i;
+       int i, listnum;
 
        info = (struct chunk_info *)r->size;
        if (info->canary != d->canary1)
@@ -994,16 +996,18 @@ free_bytes(struct dir_info *d, struct region_info *r, void *ptr)
        info->bits[i / MALLOC_BITS] |= 1U << (i % MALLOC_BITS);
        info->free++;
 
-       if (info->size != 0)
-               mp = d->chunk_dir + info->shift;
-       else
-               mp = d->chunk_dir;
-
        if (info->free == 1) {
                /* Page became non-full */
+               listnum = getrbyte() % MALLOC_CHUNK_LISTS;
+               if (info->size != 0)
+                       mp = &d->chunk_dir[info->shift][listnum];
+               else
+                       mp = &d->chunk_dir[0][listnum];
+
                LIST_INSERT_HEAD(mp, info, entries);
                return;
        }
+
        if (info->free != info->total)
                return;