/* Implement a cached obstack.
- Written by Fred Fish (fnf@cygnus.com)
- Copyright 1995 Free Software Foundation, Inc.
+ Written by Fred Fish <fnf@cygnus.com>
+ Rewritten by Jim Blandy <jimb@cygnus.com>
-This file is part of GDB.
+ Copyright 1999, 2000, 2002, 2003 Free Software Foundation, Inc.
-This program is free software; you can redistribute it and/or modify
-it under the terms of the GNU General Public License as published by
-the Free Software Foundation; either version 2 of the License, or
-(at your option) any later version.
+ This file is part of GDB.
-This program is distributed in the hope that it will be useful,
-but WITHOUT ANY WARRANTY; without even the implied warranty of
-MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
-GNU General Public License for more details.
+ This program is free software; you can redistribute it and/or modify
+ it under the terms of the GNU General Public License as published by
+ the Free Software Foundation; either version 2 of the License, or
+ (at your option) any later version.
-You should have received a copy of the GNU General Public License
-along with this program; if not, write to the Free Software
-Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA. */
+ This program is distributed in the hope that it will be useful,
+ but WITHOUT ANY WARRANTY; without even the implied warranty of
+ MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ GNU General Public License for more details.
+
+ You should have received a copy of the GNU General Public License
+ along with this program; if not, write to the Free Software
+ Foundation, Inc., 59 Temple Place - Suite 330,
+ Boston, MA 02111-1307, USA. */
#include "defs.h"
-#include "obstack.h"
+#include "gdb_obstack.h"
#include "bcache.h"
#include "gdb_string.h" /* For memcpy declaration */
+#include "gdb_assert.h"
-static unsigned int hash PARAMS ((void *, int));
-static void *lookup_cache PARAMS ((void *, int, int, struct bcache *));
+#include <stddef.h>
+#include <stdlib.h>
-/* FIXME: Incredibly simplistic hash generator. Probably way too expensive
- (consider long strings) and unlikely to have good distribution across hash
- values for typical input. */
+/* The type used to hold a single bcache string. The user data is
+ stored in d.data. Since it can be any type, it needs to have the
+ same alignment as the most strict alignment of any type on the host
+ machine. I don't know of any really correct way to do this in
+ stock ANSI C, so just do it the same way obstack.h does. */
-static unsigned int
-hash (bytes, count)
- void *bytes;
- int count;
+struct bstring
{
- unsigned int len;
- unsigned long hashval;
- unsigned int c;
- const unsigned char *data = bytes;
-
- hashval = 0;
- len = 0;
- while (count-- > 0)
- {
- c = *data++;
- hashval += c + (c << 17);
- hashval ^= hashval >> 2;
- ++len;
- }
- hashval += len + (len << 17);
- hashval ^= hashval >> 2;
- return (hashval % BCACHE_HASHSIZE);
+ struct bstring *next;
+ size_t length;
+
+ union
+ {
+ char data[1];
+ double dummy;
+ }
+ d;
+};
+
+
+/* The structure for a bcache itself. The bcache is initialized, in
+ bcache_xmalloc(), by filling it with zeros and then setting the
+ corresponding obstack's malloc() and free() methods. */
+
+struct bcache
+{
+ /* All the bstrings are allocated here. */
+ struct obstack cache;
+
+ /* How many hash buckets we're using. */
+ unsigned int num_buckets;
+
+ /* Hash buckets. This table is allocated using malloc, so when we
+ grow the table we can return the old table to the system. */
+ struct bstring **bucket;
+
+ /* Statistics. */
+ unsigned long unique_count; /* number of unique strings */
+ long total_count; /* total number of strings cached, including dups */
+ long unique_size; /* size of unique strings, in bytes */
+ long total_size; /* total number of bytes cached, including dups */
+ long structure_size; /* total size of bcache, including infrastructure */
+ /* Number of times that the hash table is expanded and hence
+ re-built, and the corresponding number of times that a string is
+ [re]hashed as part of entering it into the expanded table. The
+ total number of hashes can be computed by adding TOTAL_COUNT to
+ expand_hash_count. */
+ unsigned long expand_count;
+ unsigned long expand_hash_count;
+};
+
+/* The old hash function was stolen from SDBM. This is what DB 3.0 uses now,
+ * and is better than the old one.
+ */
+\f
+unsigned long
+hash(const void *addr, int length)
+{
+ const unsigned char *k, *e;
+ unsigned long h;
+
+ k = (const unsigned char *)addr;
+ e = k+length;
+ for (h=0; k< e;++k)
+ {
+ h *=16777619;
+ h ^= *k;
+ }
+ return (h);
}
+\f
+/* Growing the bcache's hash table. */
-static void *
-lookup_cache (bytes, count, hashval, bcachep)
- void *bytes;
- int count;
- int hashval;
- struct bcache *bcachep;
+/* If the average chain length grows beyond this, then we want to
+ resize our hash table. */
+#define CHAIN_LENGTH_THRESHOLD (5)
+
+static void
+expand_hash_table (struct bcache *bcache)
{
- void *location = NULL;
- struct hashlink **hashtablep;
- struct hashlink *linkp;
+ /* A table of good hash table sizes. Whenever we grow, we pick the
+ next larger size from this table. sizes[i] is close to 1 << (i+10),
+ so we roughly double the table size each time. After we fall off
+ the end of this table, we just double. Don't laugh --- there have
+ been executables sighted with a gigabyte of debug info. */
+ static unsigned long sizes[] = {
+ 1021, 2053, 4099, 8191, 16381, 32771,
+ 65537, 131071, 262144, 524287, 1048573, 2097143,
+ 4194301, 8388617, 16777213, 33554467, 67108859, 134217757,
+ 268435459, 536870923, 1073741827, 2147483659UL
+ };
+ unsigned int new_num_buckets;
+ struct bstring **new_buckets;
+ unsigned int i;
+
+ /* Count the stats. Every unique item needs to be re-hashed and
+ re-entered. */
+ bcache->expand_count++;
+ bcache->expand_hash_count += bcache->unique_count;
+
+ /* Find the next size. */
+ new_num_buckets = bcache->num_buckets * 2;
+ for (i = 0; i < (sizeof (sizes) / sizeof (sizes[0])); i++)
+ if (sizes[i] > bcache->num_buckets)
+ {
+ new_num_buckets = sizes[i];
+ break;
+ }
- hashtablep = bcachep -> indextable[count];
- if (hashtablep != NULL)
+ /* Allocate the new table. */
+ {
+ size_t new_size = new_num_buckets * sizeof (new_buckets[0]);
+ new_buckets = (struct bstring **) xmalloc (new_size);
+ memset (new_buckets, 0, new_size);
+
+ bcache->structure_size -= (bcache->num_buckets
+ * sizeof (bcache->bucket[0]));
+ bcache->structure_size += new_size;
+ }
+
+ /* Rehash all existing strings. */
+ for (i = 0; i < bcache->num_buckets; i++)
{
- linkp = hashtablep[hashval];
- while (linkp != NULL)
+ struct bstring *s, *next;
+
+ for (s = bcache->bucket[i]; s; s = next)
{
- if (memcmp (BCACHE_DATA (linkp), bytes, count) == 0)
- {
- location = BCACHE_DATA (linkp);
- break;
- }
- linkp = linkp -> next;
+ struct bstring **new_bucket;
+ next = s->next;
+
+ new_bucket = &new_buckets[(hash (&s->d.data, s->length)
+ % new_num_buckets)];
+ s->next = *new_bucket;
+ *new_bucket = s;
}
}
- return (location);
+
+ /* Plug in the new table. */
+ if (bcache->bucket)
+ xfree (bcache->bucket);
+ bcache->bucket = new_buckets;
+ bcache->num_buckets = new_num_buckets;
}
+\f
+/* Looking up things in the bcache. */
+
+/* The number of bytes needed to allocate a struct bstring whose data
+ is N bytes long. */
+#define BSTRING_SIZE(n) (offsetof (struct bstring, d.data) + (n))
+
+/* Find a copy of the LENGTH bytes at ADDR in BCACHE. If BCACHE has
+ never seen those bytes before, add a copy of them to BCACHE. In
+ either case, return a pointer to BCACHE's copy of that string. */
void *
-bcache (bytes, count, bcachep)
- void *bytes;
- int count;
- struct bcache *bcachep;
+bcache (const void *addr, int length, struct bcache *bcache)
{
- int hashval;
- void *location;
- struct hashlink *newlink;
- struct hashlink **linkpp;
- struct hashlink ***hashtablepp;
+ int hash_index;
+ struct bstring *s;
- if (count >= BCACHE_MAXLENGTH)
- {
- /* Rare enough to just stash unique copies */
- location = (void *) obstack_alloc (&bcachep->cache, count);
- bcachep -> cache_bytes += count;
- memcpy (location, bytes, count);
- bcachep -> bcache_overflows++;
- }
- else
- {
- hashval = hash (bytes, count);
- location = lookup_cache (bytes, count, hashval, bcachep);
- if (location != NULL)
- {
- bcachep -> cache_savings += count;
- bcachep -> cache_hits++;
- }
- else
- {
- bcachep -> cache_misses++;
- hashtablepp = &bcachep -> indextable[count];
- if (*hashtablepp == NULL)
- {
- *hashtablepp = (struct hashlink **)
- obstack_alloc (&bcachep->cache, BCACHE_HASHSIZE * sizeof (struct hashlink *));
- bcachep -> cache_bytes += BCACHE_HASHSIZE * sizeof (struct hashlink *);
- memset (*hashtablepp, 0, BCACHE_HASHSIZE * sizeof (struct hashlink *));
- }
- linkpp = &(*hashtablepp)[hashval];
- newlink = (struct hashlink *)
- obstack_alloc (&bcachep->cache, BCACHE_DATA_ALIGNMENT + count);
- bcachep -> cache_bytes += BCACHE_DATA_ALIGNMENT + count;
- memcpy (BCACHE_DATA (newlink), bytes, count);
- newlink -> next = *linkpp;
- *linkpp = newlink;
- location = BCACHE_DATA (newlink);
- }
- }
- return (location);
+ /* If our average chain length is too high, expand the hash table. */
+ if (bcache->unique_count >= bcache->num_buckets * CHAIN_LENGTH_THRESHOLD)
+ expand_hash_table (bcache);
+
+ bcache->total_count++;
+ bcache->total_size += length;
+
+ hash_index = hash (addr, length) % bcache->num_buckets;
+
+ /* Search the hash bucket for a string identical to the caller's. */
+ for (s = bcache->bucket[hash_index]; s; s = s->next)
+ if (s->length == length
+ && ! memcmp (&s->d.data, addr, length))
+ return &s->d.data;
+
+ /* The user's string isn't in the list. Insert it after *ps. */
+ {
+ struct bstring *new
+ = obstack_alloc (&bcache->cache, BSTRING_SIZE (length));
+ memcpy (&new->d.data, addr, length);
+ new->length = length;
+ new->next = bcache->bucket[hash_index];
+ bcache->bucket[hash_index] = new;
+
+ bcache->unique_count++;
+ bcache->unique_size += length;
+ bcache->structure_size += BSTRING_SIZE (length);
+
+ return &new->d.data;
+ }
}
-#if MAINTENANCE_CMDS
+\f
+/* Allocating and freeing bcaches. */
+struct bcache *
+bcache_xmalloc (void)
+{
+ /* Allocate the bcache pre-zeroed. */
+ struct bcache *b = XCALLOC (1, struct bcache);
+ obstack_specify_allocation (&b->cache, 0, 0, xmalloc, xfree);
+ return b;
+}
+
+/* Free all the storage associated with BCACHE. */
void
-print_bcache_statistics (bcachep, id)
- struct bcache *bcachep;
- char *id;
+bcache_xfree (struct bcache *bcache)
{
- struct hashlink **hashtablep;
- struct hashlink *linkp;
- int tidx, tcount, hidx, hcount, lcount, lmax, temp, lmaxt, lmaxh;
+ if (bcache == NULL)
+ return;
+ obstack_free (&bcache->cache, 0);
+ xfree (bcache->bucket);
+ xfree (bcache);
+}
- for (lmax = lcount = tcount = hcount = tidx = 0; tidx < BCACHE_MAXLENGTH; tidx++)
- {
- hashtablep = bcachep -> indextable[tidx];
- if (hashtablep != NULL)
- {
- tcount++;
- for (hidx = 0; hidx < BCACHE_HASHSIZE; hidx++)
- {
- linkp = hashtablep[hidx];
- if (linkp != NULL)
- {
- hcount++;
- for (temp = 0; linkp != NULL; linkp = linkp -> next)
- {
- lcount++;
- temp++;
- }
- if (temp > lmax)
- {
- lmax = temp;
- lmaxt = tidx;
- lmaxh = hidx;
- }
- }
- }
- }
- }
- printf_filtered (" Cached '%s' statistics:\n", id);
- printf_filtered (" Cache hits: %d\n", bcachep -> cache_hits);
- printf_filtered (" Cache misses: %d\n", bcachep -> cache_misses);
- printf_filtered (" Cache hit ratio: ");
- if (bcachep -> cache_hits + bcachep -> cache_misses > 0)
- {
- printf_filtered ("%d%%\n", ((bcachep -> cache_hits) * 100) /
- (bcachep -> cache_hits + bcachep -> cache_misses));
- }
+
+\f
+/* Printing statistics. */
+
+static int
+compare_ints (const void *ap, const void *bp)
+{
+ /* Because we know we're comparing two ints which are positive,
+ there's no danger of overflow here. */
+ return * (int *) ap - * (int *) bp;
+}
+
+
+static void
+print_percentage (int portion, int total)
+{
+ if (total == 0)
+ printf_filtered ("(not applicable)\n");
else
- {
- printf_filtered ("(not applicable)\n");
- }
- printf_filtered (" Space used for caching: %d\n", bcachep -> cache_bytes);
- printf_filtered (" Space saved by cache hits: %d\n", bcachep -> cache_savings);
- printf_filtered (" Number of bcache overflows: %d\n", bcachep -> bcache_overflows);
- printf_filtered (" Number of index buckets used: %d\n", tcount);
- printf_filtered (" Number of hash table buckets used: %d\n", hcount);
- printf_filtered (" Number of chained items: %d\n", lcount);
- printf_filtered (" Average hash table population: ");
- if (tcount > 0)
- {
- printf_filtered ("%d%%\n", (hcount * 100) / (tcount * BCACHE_HASHSIZE));
- }
+ printf_filtered ("%3d%%\n", portion * 100 / total);
+}
+
+
+/* Print statistics on BCACHE's memory usage and efficacity at
+ eliminating duplication. NAME should describe the kind of data
+ BCACHE holds. Statistics are printed using `printf_filtered' and
+ its ilk. */
+void
+print_bcache_statistics (struct bcache *c, char *type)
+{
+ int occupied_buckets;
+ int max_chain_length;
+ int median_chain_length;
+ int max_entry_size;
+ int median_entry_size;
+
+ /* Count the number of occupied buckets, tally the various string
+ lengths, and measure chain lengths. */
+ {
+ unsigned int b;
+ int *chain_length = XCALLOC (c->num_buckets + 1, int);
+ int *entry_size = XCALLOC (c->unique_count + 1, int);
+ int stringi = 0;
+
+ occupied_buckets = 0;
+
+ for (b = 0; b < c->num_buckets; b++)
+ {
+ struct bstring *s = c->bucket[b];
+
+ chain_length[b] = 0;
+
+ if (s)
+ {
+ occupied_buckets++;
+
+ while (s)
+ {
+ gdb_assert (b < c->num_buckets);
+ chain_length[b]++;
+ gdb_assert (stringi < c->unique_count);
+ entry_size[stringi++] = s->length;
+ s = s->next;
+ }
+ }
+ }
+
+ /* To compute the median, we need the set of chain lengths sorted. */
+ qsort (chain_length, c->num_buckets, sizeof (chain_length[0]),
+ compare_ints);
+ qsort (entry_size, c->unique_count, sizeof (entry_size[0]),
+ compare_ints);
+
+ if (c->num_buckets > 0)
+ {
+ max_chain_length = chain_length[c->num_buckets - 1];
+ median_chain_length = chain_length[c->num_buckets / 2];
+ }
+ else
+ {
+ max_chain_length = 0;
+ median_chain_length = 0;
+ }
+ if (c->unique_count > 0)
+ {
+ max_entry_size = entry_size[c->unique_count - 1];
+ median_entry_size = entry_size[c->unique_count / 2];
+ }
+ else
+ {
+ max_entry_size = 0;
+ median_entry_size = 0;
+ }
+
+ xfree (chain_length);
+ xfree (entry_size);
+ }
+
+ printf_filtered (" Cached '%s' statistics:\n", type);
+ printf_filtered (" Total object count: %ld\n", c->total_count);
+ printf_filtered (" Unique object count: %lu\n", c->unique_count);
+ printf_filtered (" Percentage of duplicates, by count: ");
+ print_percentage (c->total_count - c->unique_count, c->total_count);
+ printf_filtered ("\n");
+
+ printf_filtered (" Total object size: %ld\n", c->total_size);
+ printf_filtered (" Unique object size: %ld\n", c->unique_size);
+ printf_filtered (" Percentage of duplicates, by size: ");
+ print_percentage (c->total_size - c->unique_size, c->total_size);
+ printf_filtered ("\n");
+
+ printf_filtered (" Max entry size: %d\n", max_entry_size);
+ printf_filtered (" Average entry size: ");
+ if (c->unique_count > 0)
+ printf_filtered ("%ld\n", c->unique_size / c->unique_count);
else
- {
- printf_filtered ("(not applicable)\n");
- }
- printf_filtered (" Average chain length ");
- if (hcount > 0)
- {
- printf_filtered ("%d\n", lcount / hcount);
- }
+ printf_filtered ("(not applicable)\n");
+ printf_filtered (" Median entry size: %d\n", median_entry_size);
+ printf_filtered ("\n");
+
+ printf_filtered (" Total memory used by bcache, including overhead: %ld\n",
+ c->structure_size);
+ printf_filtered (" Percentage memory overhead: ");
+ print_percentage (c->structure_size - c->unique_size, c->unique_size);
+ printf_filtered (" Net memory savings: ");
+ print_percentage (c->total_size - c->structure_size, c->total_size);
+ printf_filtered ("\n");
+
+ printf_filtered (" Hash table size: %3d\n", c->num_buckets);
+ printf_filtered (" Hash table expands: %lu\n",
+ c->expand_count);
+ printf_filtered (" Hash table hashes: %lu\n",
+ c->total_count + c->expand_hash_count);
+ printf_filtered (" Hash table population: ");
+ print_percentage (occupied_buckets, c->num_buckets);
+ printf_filtered (" Median hash chain length: %3d\n",
+ median_chain_length);
+ printf_filtered (" Average hash chain length: ");
+ if (c->num_buckets > 0)
+ printf_filtered ("%3lu\n", c->unique_count / c->num_buckets);
else
- {
- printf_filtered ("(not applicable)\n");
- }
- printf_filtered (" Maximum chain length %d at %d:%d\n", lmax, lmaxt, lmaxh);
+ printf_filtered ("(not applicable)\n");
+ printf_filtered (" Maximum hash chain length: %3d\n", max_chain_length);
+ printf_filtered ("\n");
}
-#endif /* MAINTENANCE_CMDS */
+int
+bcache_memory_used (struct bcache *bcache)
+{
+ return obstack_memory_used (&bcache->cache);
+}
projects / deliverable / binutils-gdb.git / blobdiff