X-Git-Url: http://git.efficios.com/?a=blobdiff_plain;f=gdb%2Fbcache.c;h=348ad152f64f3ebb145c38f45e752030dd029bda;hb=cedfc77485dbb566619dc1e2d729ce0a70d1a4ad;hp=0d6d2058e7813aace6436e70e0b567fdf8c18376;hpb=5b64ad42d36e6d487e1f7287d37fbc243a178e72;p=deliverable%2Fbinutils-gdb.git diff --git a/gdb/bcache.c b/gdb/bcache.c index 0d6d2058e7..348ad152f6 100644 --- a/gdb/bcache.c +++ b/gdb/bcache.c @@ -1,215 +1,384 @@ /* Implement a cached obstack. - Written by Fred Fish (fnf@cygnus.com) - Copyright 1995, 1998 Free Software Foundation, Inc. + Written by Fred Fish + Rewritten by Jim Blandy -This file is part of GDB. + Copyright (C) 1999-2019 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 3 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, see . */ #include "defs.h" -#include "obstack.h" +#include "gdb_obstack.h" #include "bcache.h" -#include "gdb_string.h" /* For memcpy declaration */ - -/* Prototypes for local functions. */ -static unsigned int hash PARAMS ((void *, int)); +#include -static void *lookup_cache PARAMS ((void *, int, int, struct bcache *)); +namespace gdb { -/* 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); -} + /* Hash chain. */ + struct bstring *next; + /* 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 + { + char data[1]; + double dummy; + } + d; +}; -static void * -lookup_cache (bytes, count, hashval, bcachep) - void *bytes; - int count; - int hashval; - struct bcache *bcachep; + +/* Growing the bcache's hash table. */ + +/* If the average chain length grows beyond this, then we want to + resize our hash table. */ +#define CHAIN_LENGTH_THRESHOLD (5) + +void +bcache::expand_hash_table () { - 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. */ + m_expand_count++; + m_expand_hash_count += m_unique_count; + + /* Find the next size. */ + new_num_buckets = m_num_buckets * 2; + for (i = 0; i < (sizeof (sizes) / sizeof (sizes[0])); i++) + if (sizes[i] > m_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); + + m_structure_size -= m_num_buckets * sizeof (m_bucket[0]); + m_structure_size += new_size; + } + + /* Rehash all existing strings. */ + for (i = 0; i < m_num_buckets; i++) { - linkp = hashtablep[hashval]; - while (linkp != NULL) + struct bstring *s, *next; + + for (s = m_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[(m_hash_function (&s->d.data, s->length) + % new_num_buckets)]; + s->next = *new_bucket; + *new_bucket = s; } } - return (location); + + /* Plug in the new table. */ + xfree (m_bucket); + m_bucket = new_buckets; + m_num_buckets = new_num_buckets; } -void * -bcache (bytes, count, bcachep) - void *bytes; - int count; - struct bcache *bcachep; + +/* 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. If + optional ADDED is not NULL, return 1 in case of new entry or 0 if + returning an old entry. */ + +const void * +bcache::insert (const void *addr, int length, int *added) { - int hashval; - void *location; - struct hashlink *newlink; - struct hashlink **linkpp; - struct hashlink ***hashtablepp; + unsigned long full_hash; + unsigned short half_hash; + int hash_index; + struct bstring *s; + + if (added) + *added = 0; - if (count >= BCACHE_MAXLENGTH) + /* Lazily initialize the obstack. This can save quite a bit of + memory in some cases. */ + if (m_total_count == 0) { - /* 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++; + /* We could use obstack_specify_allocation here instead, but + gdb_obstack.h specifies the allocation/deallocation + functions. */ + obstack_init (&m_cache); } - else + + /* If our average chain length is too high, expand the hash table. */ + if (m_unique_count >= m_num_buckets * CHAIN_LENGTH_THRESHOLD) + expand_hash_table (); + + m_total_count++; + m_total_size += length; + + full_hash = m_hash_function (addr, length); + + half_hash = (full_hash >> 16); + hash_index = full_hash % m_num_buckets; + + /* Search the hash m_bucket for a string identical to the caller's. + As a short-circuit first compare the upper part of each hash + values. */ + for (s = m_bucket[hash_index]; s; s = s->next) { - hashval = hash (bytes, count); - location = lookup_cache (bytes, count, hashval, bcachep); - if (location != NULL) - { - bcachep -> cache_savings += count; - bcachep -> cache_hits++; - } - else + if (s->half_hash == half_hash) { - 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); + if (s->length == length + && m_compare_function (&s->d.data, addr, length)) + return &s->d.data; + else + m_half_hash_miss_count++; } } - return (location); + + /* The user's string isn't in the list. Insert it after *ps. */ + { + struct bstring *newobj + = (struct bstring *) obstack_alloc (&m_cache, + BSTRING_SIZE (length)); + + memcpy (&newobj->d.data, addr, length); + newobj->length = length; + newobj->next = m_bucket[hash_index]; + newobj->half_hash = half_hash; + m_bucket[hash_index] = newobj; + + m_unique_count++; + m_unique_size += length; + m_structure_size += BSTRING_SIZE (length); + + if (added) + *added = 1; + + return &newobj->d.data; + } } + -void -print_bcache_statistics (bcachep, id) - struct bcache *bcachep; - char *id; +/* Compare the byte string at ADDR1 of lenght LENGHT to the + string at ADDR2. Return 1 if they are equal. */ + +int +bcache::compare (const void *addr1, const void *addr2, int length) { - struct hashlink **hashtablep; - struct hashlink *linkp; - int tidx, tcount, hidx, hcount, lcount, lmax, temp, lmaxt, lmaxh; + return memcmp (addr1, addr2, length) == 0; +} - 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)); - } +/* Free all the storage associated with BCACHE. */ +bcache::~bcache () +{ + /* Only free the obstack if we actually initialized it. */ + if (m_total_count > 0) + obstack_free (&m_cache, 0); + xfree (m_bucket); +} + + + +/* Printing statistics. */ + +static void +print_percentage (int portion, int total) +{ + if (total == 0) + /* i18n: Like "Percentage of duplicates, by count: (not applicable)". */ + 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", (int) (portion * 100.0 / 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 +bcache::print_statistics (const 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 = XCNEWVEC (int, m_num_buckets + 1); + int *entry_size = XCNEWVEC (int, m_unique_count + 1); + int stringi = 0; + + occupied_buckets = 0; + + for (b = 0; b < m_num_buckets; b++) + { + struct bstring *s = m_bucket[b]; + + chain_length[b] = 0; + + if (s) + { + occupied_buckets++; + + while (s) + { + gdb_assert (b < m_num_buckets); + chain_length[b]++; + gdb_assert (stringi < m_unique_count); + entry_size[stringi++] = s->length; + s = s->next; + } + } + } + + /* To compute the median, we need the set of chain lengths + sorted. */ + std::sort (chain_length, chain_length + m_num_buckets); + std::sort (entry_size, entry_size + m_unique_count); + + if (m_num_buckets > 0) + { + max_chain_length = chain_length[m_num_buckets - 1]; + median_chain_length = chain_length[m_num_buckets / 2]; + } + else + { + max_chain_length = 0; + median_chain_length = 0; + } + if (m_unique_count > 0) + { + max_entry_size = entry_size[m_unique_count - 1]; + median_entry_size = entry_size[m_unique_count / 2]; + } + else + { + max_entry_size = 0; + median_entry_size = 0; + } + + xfree (chain_length); + xfree (entry_size); + } + + printf_filtered (_(" M_Cached '%s' statistics:\n"), type); + printf_filtered (_(" Total object count: %ld\n"), m_total_count); + printf_filtered (_(" Unique object count: %lu\n"), m_unique_count); + printf_filtered (_(" Percentage of duplicates, by count: ")); + print_percentage (m_total_count - m_unique_count, m_total_count); + printf_filtered ("\n"); + + printf_filtered (_(" Total object size: %ld\n"), m_total_size); + printf_filtered (_(" Unique object size: %ld\n"), m_unique_size); + printf_filtered (_(" Percentage of duplicates, by size: ")); + print_percentage (m_total_size - m_unique_size, m_total_size); + printf_filtered ("\n"); + + printf_filtered (_(" Max entry size: %d\n"), max_entry_size); + printf_filtered (_(" Average entry size: ")); + if (m_unique_count > 0) + printf_filtered ("%ld\n", m_unique_size / m_unique_count); else - { - printf_filtered ("(not applicable)\n"); - } - printf_filtered (" Average chain length "); - if (hcount > 0) - { - printf_filtered ("%d\n", lcount / hcount); - } + /* 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"), + m_structure_size); + printf_filtered (_(" Percentage memory overhead: ")); + print_percentage (m_structure_size - m_unique_size, m_unique_size); + printf_filtered (_(" Net memory savings: ")); + print_percentage (m_total_size - m_structure_size, m_total_size); + printf_filtered ("\n"); + + printf_filtered (_(" Hash table size: %3d\n"), + m_num_buckets); + printf_filtered (_(" Hash table expands: %lu\n"), + m_expand_count); + printf_filtered (_(" Hash table hashes: %lu\n"), + m_total_count + m_expand_hash_count); + printf_filtered (_(" Half hash misses: %lu\n"), + m_half_hash_miss_count); + printf_filtered (_(" Hash table population: ")); + print_percentage (occupied_buckets, m_num_buckets); + printf_filtered (_(" Median hash chain length: %3d\n"), + median_chain_length); + printf_filtered (_(" Average hash chain length: ")); + if (m_num_buckets > 0) + printf_filtered ("%3lu\n", m_unique_count / m_num_buckets); else - { - printf_filtered ("(not applicable)\n"); - } - printf_filtered (" Maximum chain length %d at %d:%d\n", lmax, lmaxt, lmaxh); + /* 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 () +{ + if (m_total_count == 0) + return 0; + return obstack_memory_used (&m_cache); +} + +} /* namespace gdb */