Written by Fred Fish <fnf@cygnus.com>
Rewritten by Jim Blandy <jimb@cygnus.com>
- Copyright 1999, 2000, 2002 Free Software Foundation, Inc.
+ Copyright (C) 1999-2016 Free Software Foundation, Inc.
This file is part of GDB.
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
+ the Free Software Foundation; either version 3 of the License, or
(at your option) any later version.
This program is distributed in the hope that it will be useful,
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. */
+ along with this program. If not, see <http://www.gnu.org/licenses/>. */
#include "defs.h"
#include "gdb_obstack.h"
#include "bcache.h"
-#include "gdb_string.h" /* For memcpy declaration */
-
-#include <stddef.h>
-#include <stdlib.h>
/* 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
struct bstring
{
+ /* Hash chain. */
struct bstring *next;
- size_t length;
+ /* Assume the data length is no more than 64k. */
+ unsigned short length;
+ /* The half hash hack. This contains the upper 16 bits of the hash
+ value and is used as a pre-check when comparing two strings and
+ avoids the need to do length or memcmp calls. It proves to be
+ roughly 100% effective. */
+ unsigned short half_hash;
union
{
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;
+ /* Number of times that the half-hash compare hit (compare the upper
+ 16 bits of hash values) hit, but the corresponding combined
+ length/data compare missed. */
+ unsigned long half_hash_miss_count;
+
+ /* Hash function to be used for this bcache object. */
+ unsigned long (*hash_function)(const void *addr, int length);
+
+ /* Compare function to be used for this bcache object. */
+ int (*compare_function)(const void *, const void *, int length);
};
-/* The old hash function was stolen from SDBM. This is what DB 3.0 uses now,
- * and is better than the old one.
- */
+/* 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);
+ return hash_continue (addr, length, 0);
+}
+
+/* Continue the calculation of the hash H at the given address. */
+
+unsigned long
+hash_continue (const void *addr, int length, unsigned long h)
+{
+ const unsigned char *k, *e;
+
+ k = (const unsigned char *)addr;
+ e = k+length;
+ for (; k< e;++k)
+ {
+ h *=16777619;
+ h ^= *k;
+ }
+ return (h);
}
\f
/* Growing the bcache's hash table. */
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++)
/* 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);
struct bstring **new_bucket;
next = s->next;
- new_bucket = &new_buckets[(hash (&s->d.data, s->length)
+ new_bucket = &new_buckets[(bcache->hash_function (&s->d.data,
+ s->length)
% new_num_buckets)];
s->next = *new_bucket;
*new_bucket = s;
/* 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 (const void *addr, int length, struct bcache *bcache)
+const void *
+bcache (const void *addr, int length, struct bcache *cache)
{
+ return bcache_full (addr, length, cache, NULL);
+}
+
+/* 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. If
+ optional ADDED is not NULL, return 1 in case of new entry or 0 if
+ returning an old entry. */
+
+const void *
+bcache_full (const void *addr, int length, struct bcache *bcache, int *added)
+{
+ unsigned long full_hash;
+ unsigned short half_hash;
int hash_index;
struct bstring *s;
+ if (added)
+ *added = 0;
+
+ /* Lazily initialize the obstack. This can save quite a bit of
+ memory in some cases. */
+ if (bcache->total_count == 0)
+ {
+ /* We could use obstack_specify_allocation here instead, but
+ gdb_obstack.h specifies the allocation/deallocation
+ functions. */
+ obstack_init (&bcache->cache);
+ }
+
/* 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;
+ full_hash = bcache->hash_function (addr, length);
- /* Search the hash bucket for a string identical to the caller's. */
+ half_hash = (full_hash >> 16);
+ hash_index = full_hash % bcache->num_buckets;
+
+ /* Search the hash bucket for a string identical to the caller's.
+ As a short-circuit first compare the upper part of each hash
+ values. */
for (s = bcache->bucket[hash_index]; s; s = s->next)
- if (s->length == length
- && ! memcmp (&s->d.data, addr, length))
- return &s->d.data;
+ {
+ if (s->half_hash == half_hash)
+ {
+ if (s->length == length
+ && bcache->compare_function (&s->d.data, addr, length))
+ return &s->d.data;
+ else
+ bcache->half_hash_miss_count++;
+ }
+ }
/* 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;
+ struct bstring *newobj
+ = (struct bstring *) obstack_alloc (&bcache->cache,
+ BSTRING_SIZE (length));
+
+ memcpy (&newobj->d.data, addr, length);
+ newobj->length = length;
+ newobj->next = bcache->bucket[hash_index];
+ newobj->half_hash = half_hash;
+ bcache->bucket[hash_index] = newobj;
bcache->unique_count++;
bcache->unique_size += length;
bcache->structure_size += BSTRING_SIZE (length);
- return &new->d.data;
+ if (added)
+ *added = 1;
+
+ return &newobj->d.data;
}
}
-
\f
+
+/* Compare the byte string at ADDR1 of lenght LENGHT to the
+ string at ADDR2. Return 1 if they are equal. */
+
+static int
+bcache_compare (const void *addr1, const void *addr2, int length)
+{
+ return memcmp (addr1, addr2, length) == 0;
+}
+
/* Allocating and freeing bcaches. */
+/* Allocated a bcache. HASH_FUNCTION and COMPARE_FUNCTION can be used
+ to pass in custom hash, and compare functions to be used by this
+ bcache. If HASH_FUNCTION is NULL hash() is used and if
+ COMPARE_FUNCTION is NULL memcmp() is used. */
+
struct bcache *
-bcache_xmalloc (void)
+bcache_xmalloc (unsigned long (*hash_function)(const void *, int length),
+ int (*compare_function)(const void *,
+ const void *,
+ int length))
{
/* Allocate the bcache pre-zeroed. */
- struct bcache *b = XCALLOC (1, struct bcache);
- obstack_specify_allocation (&b->cache, 0, 0, xmalloc, xfree);
+ struct bcache *b = XCNEW (struct bcache);
+
+ if (hash_function)
+ b->hash_function = hash_function;
+ else
+ b->hash_function = hash;
+
+ if (compare_function)
+ b->compare_function = compare_function;
+ else
+ b->compare_function = bcache_compare;
return b;
}
{
if (bcache == NULL)
return;
- obstack_free (&bcache->cache, 0);
+ /* Only free the obstack if we actually initialized it. */
+ if (bcache->total_count > 0)
+ obstack_free (&bcache->cache, 0);
xfree (bcache->bucket);
xfree (bcache);
}
\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");
+ /* i18n: Like "Percentage of duplicates, by count: (not applicable)". */
+ printf_filtered (_("(not applicable)\n"));
else
- printf_filtered ("%3d%%\n", portion * 100 / total);
+ printf_filtered ("%3d%%\n", (int) (portion * 100.0 / total));
}
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, and measure chain lengths. */
+ /* Count the number of occupied buckets, tally the various string
+ lengths, and measure chain lengths. */
{
unsigned int b;
- int *chain_length
- = (int *) alloca (c->num_buckets * sizeof (*chain_length));
+ int *chain_length = XCNEWVEC (int, c->num_buckets + 1);
+ int *entry_size = XCNEWVEC (int, c->unique_count + 1);
+ int stringi = 0;
occupied_buckets = 0;
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. */
+ /* To compute the median, we need the set of chain lengths
+ sorted. */
qsort (chain_length, c->num_buckets, sizeof (chain_length[0]),
- compare_ints);
+ compare_positive_ints);
+ qsort (entry_size, c->unique_count, sizeof (entry_size[0]),
+ compare_positive_ints);
if (c->num_buckets > 0)
{
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: ");
+ 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: ");
+ 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 (" Total memory used by bcache, including overhead: %ld\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
+ /* i18n: "Average entry size: (not applicable)". */
+ 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: ");
+ printf_filtered (_(" Percentage memory overhead: "));
print_percentage (c->structure_size - c->unique_size, c->unique_size);
- printf_filtered (" Net memory savings: ");
+ 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 population: ");
+ 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 (_(" Half hash misses: %lu\n"),
+ c->half_hash_miss_count);
+ printf_filtered (_(" Hash table population: "));
print_percentage (occupied_buckets, c->num_buckets);
- printf_filtered (" Median hash chain length: %3d\n",
+ printf_filtered (_(" Median hash chain length: %3d\n"),
median_chain_length);
- printf_filtered (" Average hash 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 hash chain length: %3d\n", max_chain_length);
+ /* i18n: "Average hash chain length: (not applicable)". */
+ printf_filtered (_("(not applicable)\n"));
+ printf_filtered (_(" Maximum hash chain length: %3d\n"),
+ max_chain_length);
printf_filtered ("\n");
}
int
bcache_memory_used (struct bcache *bcache)
{
+ if (bcache->total_count == 0)
+ return 0;
return obstack_memory_used (&bcache->cache);
}
projects / deliverable / binutils-gdb.git / blobdiff