Re: [PATCH] symbol lookup cache

Doug Evans
2015-01-11T19:11:24Z

Joel Brobecker <brobecker@adacore.com> writes:
>> But, *if* one-size-fits-all *wasn't* working (*1), and I think I can
>> reasonably assume we're agreed we're not there yet, then would you
>> immediately go the route of providing a user option to allow changing
>> the size, or first see if gdb could do better on its own?
>>
>> ---
>> (*1): I'm only suggesting exploring dynamically adjusting the cache
>> size (I realize you wrote hash size) *if* the data suggests we need
>> it. IMO we're not there yet. But, and here's where the disagreement
>> is (AFAICT), *if* we do get there, I'd rather see if gdb could do
>> better on its own first, before adding a knob that the user has to
>> tweak to get the desired performance.
>
> On that, I don't really have an opinion, at least not yet; and since
> I don't see us getting there, I propose we do not decide now :).

Hi.

Here's what I committed.
[regression tested again on amd64-linux]

I have a couple of followup patches, which I'll get in today.

2015-01-10 Doug Evans <xdje42@gmail.com>

Add symbol lookup cache.
* NEWS: Document new options and commands.
* symtab.c (symbol_cache_key): New static global.
(DEFAULT_SYMBOL_CACHE_SIZE, MAX_SYMBOL_CACHE_SIZE): New macros.
(SYMBOL_LOOKUP_FAILED): New macro.
(symbol_cache_slot_state): New enum.
(block_symbol_cache): New struct.
(symbol_cache): New struct.
(new_symbol_cache_size, symbol_cache_size): New static globals.
(hash_symbol_entry, eq_symbol_entry): New functions.
(symbol_cache_byte_size, resize_symbol_cache): New functions.
(make_symbol_cache, free_symbol_cache): New functions.
(get_symbol_cache, symbol_cache_cleanup): New function.
(set_symbol_cache_size, set_symbol_cache_size_handler): New functions.
(symbol_cache_lookup, symbol_cache_clear_slot): New function.
(symbol_cache_mark_found, symbol_cache_mark_not_found): New functions.
(symbol_cache_flush, symbol_cache_dump): New functions.
(maintenance_print_symbol_cache): New function.
(maintenance_flush_symbol_cache): New function.
(symbol_cache_stats): New function.
(maintenance_print_symbol_cache_statistics): New function.
(symtab_new_objfile_observer): New function.
(symtab_free_objfile_observer): New function.
(lookup_static_symbol, lookup_global_symbol): Use symbol cache.
(_initialize_symtab): Init symbol_cache_key. New parameter
maint symbol-cache-size. New maint commands print symbol-cache,
print symbol-cache-statistics, flush-symbol-cache.
Install new_objfile, free_objfile observers.

doc/
* gdb.texinfo (Symbols): Document new commands
"maint print symbol-cache", "maint print symbol-cache-statistics",
"maint flush-symbol-cache". Document new option
"maint set symbol-cache-size".

diff --git a/gdb/NEWS b/gdb/NEWS
index 9a668c4..f866a5a 100644
--- a/gdb/NEWS
+++ b/gdb/NEWS
@@ -57,6 +57,15 @@ add-auto-load-scripts-directory directory
maint print user-registers
List all currently available "user" registers.

+maint print symbol-cache
+ Print the contents of the symbol cache.
+
+maint print symbol-cache-statistics
+ Print statistics of symbol cache usage.
+
+maint flush-symbol-cache
+ Flush the contents of the symbol cache.
+
compile code [-r|-raw] [--] [source code]
Compile, inject, and execute in the inferior the executable object
code produced by compiling the provided source code.
@@ -90,6 +99,10 @@ set debug symbol-lookup
show debug symbol-lookup
Control display of debugging info regarding symbol lookup.

+maint set symbol-cache-size
+maint show symbol-cache-size
+ Control the size of the symbol cache.
+
* MI changes

** The -list-thread-groups command outputs an exit-code field for
diff --git a/gdb/doc/gdb.texinfo b/gdb/doc/gdb.texinfo
index f4d7132..b752524 100644
--- a/gdb/doc/gdb.texinfo
+++ b/gdb/doc/gdb.texinfo
@@ -16471,8 +16471,39 @@ line 1574.
@}
(@value{GDBP})
@end smallexample
-@end table

+@kindex maint set symbol-cache-size
+@cindex symbol cache size
+@item maint set symbol-cache-size @var{size}
+Set the size of the symbol cache to @var{size}.
+The default size is intended to be good enough for debugging
+most applications. This option exists to allow for experimenting
+with different sizes.
+
+@kindex maint show symbol-cache-size
+@item maint show symbol-cache-size
+Show the size of the symbol cache.
+
+@kindex maint print symbol-cache
+@cindex symbol cache, printing its contents
+@item maint print symbol-cache
+Print the contents of the symbol cache.
+This is useful when debugging symbol cache issues.
+
+@kindex maint print symbol-cache-statistics
+@cindex symbol cache, printing usage statistics
+@item maint print symbol-cache-statistics
+Print symbol cache usage statistics.
+This helps determine how well the cache is being utilized.
+
+@kindex maint flush-symbol-cache
+@cindex symbol cache, flushing
+@item maint flush-symbol-cache
+Flush the contents of the symbol cache, all entries are removed.
+This command is useful when debugging the symbol cache.
+It is also useful when collecting performance data.
+
+@end table

@node Altering
@chapter Altering Execution
diff --git a/gdb/symtab.c b/gdb/symtab.c
index b5d8d63..7193131 100644
--- a/gdb/symtab.c
+++ b/gdb/symtab.c
@@ -102,12 +102,115 @@ struct main_info
enum language language_of_main;
};

+/* Program space key for finding its symbol cache. */
+
+static const struct program_space_data *symbol_cache_key;
+
+/* The default symbol cache size.
+ There is no extra cpu cost for large N (except when flushing the cache,
+ which is rare). The value here is just a first attempt. A better default
+ value may be higher or lower. A prime number can make up for a bad hash
+ computation, so that's why the number is what it is. */
+#define DEFAULT_SYMBOL_CACHE_SIZE 1021
+
+/* The maximum symbol cache size.
+ There's no method to the decision of what value to use here, other than
+ there's no point in allowing a user typo to make gdb consume all memory. */
+#define MAX_SYMBOL_CACHE_SIZE (1024*1024)
+
+/* symbol_cache_lookup returns this if a previous lookup failed to find the
+ symbol in any objfile. */
+#define SYMBOL_LOOKUP_FAILED ((struct symbol *) 1)
+
+/* Recording lookups that don't find the symbol is just as important, if not
+ more so, than recording found symbols. */
+
+enum symbol_cache_slot_state
+{
+ SYMBOL_SLOT_UNUSED,
+ SYMBOL_SLOT_NOT_FOUND,
+ SYMBOL_SLOT_FOUND
+};
+
+/* Symbols don't specify global vs static block.
+ So keep them in separate caches. */
+
+struct block_symbol_cache
+{
+ unsigned int hits;
+ unsigned int misses;
+ unsigned int collisions;
+
+ /* SYMBOLS is a variable length array of this size.
+ One can imagine that in general one cache (global/static) should be a
+ fraction of the size of the other, but there's no data at the moment
+ on which to decide. */
+ unsigned int size;
+
+ struct symbol_cache_slot
+ {
+ enum symbol_cache_slot_state state;
+
+ /* The objfile that was current when the symbol was looked up.
+ This is only needed for global blocks, but for simplicity's sake
+ we allocate the space for both. If data shows the extra space used
+ for static blocks is a problem, we can split things up then.
+
+ Global blocks need cache lookup to include the objfile context because
+ we need to account for gdbarch_iterate_over_objfiles_in_search_order
+ which can traverse objfiles in, effectively, any order, depending on
+ the current objfile, thus affecting which symbol is found. Normally,
+ only the current objfile is searched first, and then the rest are
+ searched in recorded order; but putting cache lookup inside
+ gdbarch_iterate_over_objfiles_in_search_order would be awkward.
+ Instead we just make the current objfile part of the context of
+ cache lookup. This means we can record the same symbol multiple times,
+ each with a different "current objfile" that was in effect when the
+ lookup was saved in the cache, but cache space is pretty cheap. */
+ const struct objfile *objfile_context;
+
+ union
+ {
+ struct symbol *found;
+ struct
+ {
+ char *name;
+ domain_enum domain;
+ } not_found;
+ } value;
+ } symbols[1];
+};
+
+/* The symbol cache.
+
+ Searching for symbols in the static and global blocks over multiple objfiles
+ again and again can be slow, as can searching very big objfiles. This is a
+ simple cache to improve symbol lookup performance, which is critical to
+ overall gdb performance.
+
+ Symbols are hashed on the name, its domain, and block.
+ They are also hashed on their objfile for objfile-specific lookups. */
+
+struct symbol_cache
+{
+ struct block_symbol_cache *global_symbols;
+ struct block_symbol_cache *static_symbols;
+};
+
/* When non-zero, print debugging messages related to symtab creation. */
unsigned int symtab_create_debug = 0;

/* When non-zero, print debugging messages related to symbol lookup. */
unsigned int symbol_lookup_debug = 0;

+/* The size of the cache is staged here. */
+static unsigned int new_symbol_cache_size = DEFAULT_SYMBOL_CACHE_SIZE;
+
+/* The current value of the symbol cache size.
+ This is saved so that if the user enters a value too big we can restore
+ the original value from here. */
+static unsigned int symbol_cache_size = DEFAULT_SYMBOL_CACHE_SIZE;
+
/* Non-zero if a file may be known by two different basenames.
This is the uncommon case, and significantly slows down gdb.
Default set to "off" to not slow down the common case. */
@@ -1058,6 +1161,520 @@ expand_symtab_containing_pc (CORE_ADDR pc, struct obj_section *section)
}
}
\f
+/* Hash function for the symbol cache. */
+
+static unsigned int
+hash_symbol_entry (const struct objfile *objfile_context,
+ const char *name, domain_enum domain)
+{
+ unsigned int hash = (uintptr_t) objfile_context;
+
+ if (name != NULL)
+ hash += htab_hash_string (name);
+
+ hash += domain;
+
+ return hash;
+}
+
+/* Equality function for the symbol cache. */
+
+static int
+eq_symbol_entry (const struct symbol_cache_slot *slot,
+ const struct objfile *objfile_context,
+ const char *name, domain_enum domain)
+{
+ const char *slot_name;
+ domain_enum slot_domain;
+
+ if (slot->state == SYMBOL_SLOT_UNUSED)
+ return 0;
+
+ if (slot->objfile_context != objfile_context)
+ return 0;
+
+ if (slot->state == SYMBOL_SLOT_NOT_FOUND)
+ {
+ slot_name = slot->value.not_found.name;
+ slot_domain = slot->value.not_found.domain;
+ }
+ else
+ {
+ slot_name = SYMBOL_LINKAGE_NAME (slot->value.found);
+ slot_domain = SYMBOL_DOMAIN (slot->value.found);
+ }
+
+ /* NULL names match. */
+ if (slot_name == NULL && name == NULL)
+ ;
+ else if (slot_name != NULL && name != NULL)
+ {
+ if (strcmp (slot_name, name) != 0)
+ return 0;
+ }
+ else
+ {
+ /* Only one name is NULL. */
+ return 0;
+ }
+
+ if (slot_domain != domain)
+ return 0;
+
+ return 1;
+}
+
+/* Given a cache of size SIZE, return the size of the struct (with variable
+ length array) in bytes. */
+
+static size_t
+symbol_cache_byte_size (unsigned int size)
+{
+ return (sizeof (struct block_symbol_cache)
+ + ((size - 1) * sizeof (struct symbol_cache_slot)));
+}
+
+/* Resize CACHE. */
+
+static void
+resize_symbol_cache (struct symbol_cache *cache, unsigned int new_size)
+{
+ /* If there's no change in size, don't do anything.
+ All caches have the same size, so we can just compare with the size
+ of the global symbols cache. */
+ if ((cache->global_symbols != NULL
+ && cache->global_symbols->size == new_size)
+ || (cache->global_symbols == NULL
+ && new_size == 0))
+ return;
+
+ xfree (cache->global_symbols);
+ xfree (cache->static_symbols);
+
+ if (new_size == 0)
+ {
+ cache->global_symbols = NULL;
+ cache->static_symbols = NULL;
+ }
+ else
+ {
+ size_t total_size = symbol_cache_byte_size (new_size);
+
+ cache->global_symbols = xcalloc (1, total_size);
+ cache->static_symbols = xcalloc (1, total_size);
+ cache->global_symbols->size = new_size;
+ cache->static_symbols->size = new_size;
+ }
+}
+
+/* Make a symbol cache of size SIZE. */
+
+static struct symbol_cache *
+make_symbol_cache (unsigned int size)
+{
+ struct symbol_cache *cache;
+
+ cache = XCNEW (struct symbol_cache);
+ resize_symbol_cache (cache, symbol_cache_size);
+ return cache;
+}
+
+/* Free the space used by CACHE. */
+
+static void
+free_symbol_cache (struct symbol_cache *cache)
+{
+ xfree (cache->global_symbols);
+ xfree (cache->static_symbols);
+ xfree (cache);
+}
+
+/* Return the symbol cache of PSPACE.
+ Create one if it doesn't exist yet. */
+
+static struct symbol_cache *
+get_symbol_cache (struct program_space *pspace)
+{
+ struct symbol_cache *cache = program_space_data (pspace, symbol_cache_key);
+
+ if (cache == NULL)
+ {
+ cache = make_symbol_cache (symbol_cache_size);
+ set_program_space_data (pspace, symbol_cache_key, cache);
+ }
+
+ return cache;
+}
+
+/* Delete the symbol cache of PSPACE.
+ Called when PSPACE is destroyed. */
+
+static void
+symbol_cache_cleanup (struct program_space *pspace, void *data)
+{
+ struct symbol_cache *cache = data;
+
+ free_symbol_cache (cache);
+}
+
+/* Set the size of the symbol cache in all program spaces. */
+
+static void
+set_symbol_cache_size (unsigned int new_size)
+{
+ struct program_space *pspace;
+
+ ALL_PSPACES (pspace)
+ {
+ struct symbol_cache *cache
+ = program_space_data (pspace, symbol_cache_key);
+
+ /* The pspace could have been created but not have a cache yet. */
+ if (cache != NULL)
+ resize_symbol_cache (cache, new_size);
+ }
+}
+
+/* Called when symbol-cache-size is set. */
+
+static void
+set_symbol_cache_size_handler (char *args, int from_tty,
+ struct cmd_list_element *c)
+{
+ if (new_symbol_cache_size > MAX_SYMBOL_CACHE_SIZE)
+ {
+ /* Restore the previous value.
+ This is the value the "show" command prints. */
+ new_symbol_cache_size = symbol_cache_size;
+
+ error (_("Symbol cache size is too large, max is %u."),
+ MAX_SYMBOL_CACHE_SIZE);
+ }
+ symbol_cache_size = new_symbol_cache_size;
+
+ set_symbol_cache_size (symbol_cache_size);
+}
+
+/* Lookup symbol NAME,DOMAIN in BLOCK in the symbol cache of PSPACE.
+ OBJFILE_CONTEXT is the current objfile, which may be NULL.
+ The result is the symbol if found, SYMBOL_LOOKUP_FAILED if a previous lookup
+ failed (and thus this one will too), or NULL if the symbol is not present
+ in the cache.
+ *BSC_PTR, *SLOT_PTR are set to the cache and slot of the symbol, whether
+ found or not found. */
+
+static struct symbol *
+symbol_cache_lookup (struct symbol_cache *cache,
+ struct objfile *objfile_context, int block,
+ const char *name, domain_enum domain,
+ struct block_symbol_cache **bsc_ptr,
+ struct symbol_cache_slot **slot_ptr)
+{
+ struct block_symbol_cache *bsc;
+ unsigned int hash;
+ struct symbol_cache_slot *slot;
+
+ if (block == GLOBAL_BLOCK)
+ bsc = cache->global_symbols;
+ else
+ bsc = cache->static_symbols;
+ if (bsc == NULL)
+ {
+ *bsc_ptr = NULL;
+ *slot_ptr = NULL;
+ return NULL;
+ }
+
+ hash = hash_symbol_entry (objfile_context, name, domain);
+ slot = bsc->symbols + hash % bsc->size;
+ *bsc_ptr = bsc;
+ *slot_ptr = slot;
+
+ if (eq_symbol_entry (slot, objfile_context, name, domain))
+ {
+ if (symbol_lookup_debug)
+ fprintf_unfiltered (gdb_stdlog,
+ "%s block symbol cache hit%s for %s, %s\n",
+ block == GLOBAL_BLOCK ? "Global" : "Static",
+ slot->state == SYMBOL_SLOT_NOT_FOUND
+ ? " (not found)" : "",
+ name, domain_name (domain));
+ ++bsc->hits;
+ if (slot->state == SYMBOL_SLOT_NOT_FOUND)
+ return SYMBOL_LOOKUP_FAILED;
+ return slot->value.found;
+ }
+
+ if (symbol_lookup_debug)
+ {
+ fprintf_unfiltered (gdb_stdlog,
+ "%s block symbol cache miss for %s, %s\n",
+ block == GLOBAL_BLOCK ? "Global" : "Static",
+ name, domain_name (domain));
+ }
+ ++bsc->misses;
+ return NULL;
+}
+
+/* Clear out SLOT. */
+
+static void
+symbol_cache_clear_slot (struct symbol_cache_slot *slot)
+{
+ if (slot->state == SYMBOL_SLOT_NOT_FOUND)
+ xfree (slot->value.not_found.name);
+ slot->state = SYMBOL_SLOT_UNUSED;
+}
+
+/* Mark SYMBOL as found in SLOT. */
+
+static void
+symbol_cache_mark_found (struct block_symbol_cache *bsc,
+ struct symbol_cache_slot *slot,
+ struct objfile *objfile, struct symbol *symbol)
+{
+ if (bsc == NULL)
+ return;
+ if (slot->state != SYMBOL_SLOT_UNUSED)
+ {
+ ++bsc->collisions;
+ symbol_cache_clear_slot (slot);
+ }
+ slot->state = SYMBOL_SLOT_FOUND;
+ slot->objfile_context = objfile;
+ slot->value.found = symbol;
+}
+
+/* Mark symbol NAME, DOMAIN as not found in SLOT. */
+
+static void
+symbol_cache_mark_not_found (struct block_symbol_cache *bsc,
+ struct symbol_cache_slot *slot,
+ struct objfile *objfile_context,
+ const char *name, domain_enum domain)
+{
+ if (bsc == NULL)
+ return;
+ if (slot->state != SYMBOL_SLOT_UNUSED)
+ {
+ ++bsc->collisions;
+ symbol_cache_clear_slot (slot);
+ }
+ slot->state = SYMBOL_SLOT_NOT_FOUND;
+ slot->objfile_context = objfile_context;
+ slot->value.not_found.name = xstrdup (name);
+ slot->value.not_found.domain = domain;
+}
+
+/* Flush the symbol cache of PSPACE. */
+
+static void
+symbol_cache_flush (struct program_space *pspace)
+{
+ struct symbol_cache *cache = program_space_data (pspace, symbol_cache_key);
+ int pass;
+ size_t total_size;
+
+ if (cache == NULL)
+ return;
+ if (cache->global_symbols == NULL)
+ {
+ gdb_assert (symbol_cache_size == 0);
+ gdb_assert (cache->static_symbols == NULL);
+ return;
+ }
+
+ /* If the cache is untouched since the last flush, early exit.
+ This is important for performance during the startup of a program linked
+ with 100s (or 1000s) of shared libraries. */
+ if (cache->global_symbols->misses == 0
+ && cache->static_symbols->misses == 0)
+ return;
+
+ gdb_assert (cache->global_symbols->size == symbol_cache_size);
+ gdb_assert (cache->static_symbols->size == symbol_cache_size);
+
+ for (pass = 0; pass < 2; ++pass)
+ {
+ struct block_symbol_cache *bsc
+ = pass == 0 ? cache->global_symbols : cache->static_symbols;
+ unsigned int i;
+
+ for (i = 0; i < bsc->size; ++i)
+ symbol_cache_clear_slot (&bsc->symbols[i]);
+ }
+
+ cache->global_symbols->hits = 0;
+ cache->global_symbols->misses = 0;
+ cache->global_symbols->collisions = 0;
+ cache->static_symbols->hits = 0;
+ cache->static_symbols->misses = 0;
+ cache->static_symbols->collisions = 0;
+}
+
+/* Dump CACHE. */
+
+static void
+symbol_cache_dump (const struct symbol_cache *cache)
+{
+ int pass;
+
+ if (cache->global_symbols == NULL)
+ {
+ printf_filtered (" <disabled>\n");
+ return;
+ }
+
+ for (pass = 0; pass < 2; ++pass)
+ {
+ const struct block_symbol_cache *bsc
+ = pass == 0 ? cache->global_symbols : cache->static_symbols;
+ unsigned int i;
+
+ if (pass == 0)
+ printf_filtered ("Global symbols:\n");
+ else
+ printf_filtered ("Static symbols:\n");
+
+ for (i = 0; i < bsc->size; ++i)
+ {
+ const struct symbol_cache_slot *slot = &bsc->symbols[i];
+
+ QUIT;
+
+ switch (slot->state)
+ {
+ case SYMBOL_SLOT_UNUSED:
+ break;
+ case SYMBOL_SLOT_NOT_FOUND:
+ printf_filtered (" [%-4u] = %s, %s (not found)\n", i,
+ host_address_to_string (slot->objfile_context),
+ slot->value.not_found.name);
+ break;
+ case SYMBOL_SLOT_FOUND:
+ printf_filtered (" [%-4u] = %s, %s\n", i,
+ host_address_to_string (slot->objfile_context),
+ SYMBOL_PRINT_NAME (slot->value.found));
+ break;
+ }
+ }
+ }
+}
+
+/* The "mt print symbol-cache" command. */
+
+static void
+maintenance_print_symbol_cache (char *args, int from_tty)
+{
+ struct program_space *pspace;
+
+ ALL_PSPACES (pspace)
+ {
+ struct symbol_cache *cache;
+
+ printf_filtered (_("Symbol cache for pspace %d\n%s:\n"),
+ pspace->num,
+ pspace->symfile_object_file != NULL
+ ? objfile_name (pspace->symfile_object_file)
+ : "(no object file)");
+
+ /* If the cache hasn't been created yet, avoid creating one. */
+ cache = program_space_data (pspace, symbol_cache_key);
+ if (cache == NULL)
+ printf_filtered (" <empty>\n");
+ else
+ symbol_cache_dump (cache);
+ }
+}
+
+/* The "mt flush-symbol-cache" command. */
+
+static void
+maintenance_flush_symbol_cache (char *args, int from_tty)
+{
+ struct program_space *pspace;
+
+ ALL_PSPACES (pspace)
+ {
+ symbol_cache_flush (pspace);
+ }
+}
+
+/* Print usage statistics of CACHE. */
+
+static void
+symbol_cache_stats (struct symbol_cache *cache)
+{
+ int pass;
+
+ if (cache->global_symbols == NULL)
+ {
+ printf_filtered (" <disabled>\n");
+ return;
+ }
+
+ for (pass = 0; pass < 2; ++pass)
+ {
+ const struct block_symbol_cache *bsc
+ = pass == 0 ? cache->global_symbols : cache->static_symbols;
+
+ QUIT;
+
+ if (pass == 0)
+ printf_filtered ("Global block cache stats:\n");
+ else
+ printf_filtered ("Static block cache stats:\n");
+
+ printf_filtered (" size: %u\n", bsc->size);
+ printf_filtered (" hits: %u\n", bsc->hits);
+ printf_filtered (" misses: %u\n", bsc->misses);
+ printf_filtered (" collisions: %u\n", bsc->collisions);
+ }
+}
+
+/* The "mt print symbol-cache-statistics" command. */
+
+static void
+maintenance_print_symbol_cache_statistics (char *args, int from_tty)
+{
+ struct program_space *pspace;
+
+ ALL_PSPACES (pspace)
+ {
+ struct symbol_cache *cache;
+
+ printf_filtered (_("Symbol cache statistics for pspace %d\n%s:\n"),
+ pspace->num,
+ pspace->symfile_object_file != NULL
+ ? objfile_name (pspace->symfile_object_file)
+ : "(no object file)");
+
+ /* If the cache hasn't been created yet, avoid creating one. */
+ cache = program_space_data (pspace, symbol_cache_key);
+ if (cache == NULL)
+ printf_filtered (" empty, no stats available\n");
+ else
+ symbol_cache_stats (cache);
+ }
+}
+
+/* This module's 'new_objfile' observer. */
+
+static void
+symtab_new_objfile_observer (struct objfile *objfile)
+{
+ /* Ideally we'd use OBJFILE->pspace, but OBJFILE may be NULL. */
+ symbol_cache_flush (current_program_space);
+}
+
+/* This module's 'free_objfile' observer. */
+
+static void
+symtab_free_objfile_observer (struct objfile *objfile)
+{
+ symbol_cache_flush (objfile->pspace);
+}
+\f
/* Debug symbols usually don't have section information. We need to dig that
out of the minimal symbols and stash that in the debug symbol. */

@@ -1970,16 +2587,36 @@ lookup_symbol_in_objfile (struct objfile *objfile, int block_index,
struct symbol *
lookup_static_symbol (const char *name, const domain_enum domain)
{
+ struct symbol_cache *cache = get_symbol_cache (current_program_space);
struct objfile *objfile;
struct symbol *result;
+ struct block_symbol_cache *bsc;
+ struct symbol_cache_slot *slot;
+
+ /* Lookup in STATIC_BLOCK is not current-objfile-dependent, so just pass
+ NULL for OBJFILE_CONTEXT. */
+ result = symbol_cache_lookup (cache, NULL, STATIC_BLOCK, name, domain,
+ &bsc, &slot);
+ if (result != NULL)
+ {
+ if (result == SYMBOL_LOOKUP_FAILED)
+ return NULL;
+ return result;
+ }

ALL_OBJFILES (objfile)
{
result = lookup_symbol_in_objfile (objfile, STATIC_BLOCK, name, domain);
if (result != NULL)
- return result;
+ {
+ /* Still pass NULL for OBJFILE_CONTEXT here. */
+ symbol_cache_mark_found (bsc, slot, NULL, result);
+ return result;
+ }
}

+ /* Still pass NULL for OBJFILE_CONTEXT here. */
+ symbol_cache_mark_not_found (bsc, slot, NULL, name, domain);
return NULL;
}

@@ -2027,25 +2664,48 @@ lookup_global_symbol (const char *name,
const struct block *block,
const domain_enum domain)
{
- struct symbol *sym = NULL;
- struct objfile *objfile = NULL;
+ struct symbol_cache *cache = get_symbol_cache (current_program_space);
+ struct symbol *sym;
+ struct objfile *objfile;
struct global_sym_lookup_data lookup_data;
+ struct block_symbol_cache *bsc;
+ struct symbol_cache_slot *slot;

- /* Call library-specific lookup procedure. */
objfile = lookup_objfile_from_block (block);
+
+ /* First see if we can find the symbol in the cache.
+ This works because we use the current objfile to qualify the lookup. */
+ sym = symbol_cache_lookup (cache, objfile, GLOBAL_BLOCK, name, domain,
+ &bsc, &slot);
+ if (sym != NULL)
+ {
+ if (sym == SYMBOL_LOOKUP_FAILED)
+ return NULL;
+ return sym;
+ }
+
+ /* Call library-specific lookup procedure. */
if (objfile != NULL)
sym = solib_global_lookup (objfile, name, domain);
- if (sym != NULL)
- return sym;

- memset (&lookup_data, 0, sizeof (lookup_data));
- lookup_data.name = name;
- lookup_data.domain = domain;
- gdbarch_iterate_over_objfiles_in_search_order
- (objfile != NULL ? get_objfile_arch (objfile) : target_gdbarch (),
- lookup_symbol_global_iterator_cb, &lookup_data, objfile);
+ /* If that didn't work go a global search (of global blocks, heh). */
+ if (sym == NULL)
+ {
+ memset (&lookup_data, 0, sizeof (lookup_data));
+ lookup_data.name = name;
+ lookup_data.domain = domain;
+ gdbarch_iterate_over_objfiles_in_search_order
+ (objfile != NULL ? get_objfile_arch (objfile) : target_gdbarch (),
+ lookup_symbol_global_iterator_cb, &lookup_data, objfile);
+ sym = lookup_data.result;
+ }

- return lookup_data.result;
+ if (sym != NULL)
+ symbol_cache_mark_found (bsc, slot, objfile, sym);
+ else
+ symbol_cache_mark_not_found (bsc, slot, objfile, name, domain);
+
+ return sym;
}

int
@@ -5436,6 +6096,9 @@ _initialize_symtab (void)
main_progspace_key
= register_program_space_data_with_cleanup (NULL, main_info_cleanup);

+ symbol_cache_key
+ = register_program_space_data_with_cleanup (NULL, symbol_cache_cleanup);
+
add_info ("variables", variables_info, _("\
All global and static variable names, or those matching REGEXP."));
if (dbx_commands)
@@ -5511,5 +6174,31 @@ When enabled (non-zero), symbol lookups are logged."),
NULL, NULL,
&setdebuglist, &showdebuglist);

+ add_setshow_zuinteger_cmd ("symbol-cache-size", no_class,
+ &new_symbol_cache_size,
+ _("Set the size of the symbol cache."),
+ _("Show the size of the symbol cache."), _("\
+The size of the symbol cache.\n\
+If zero then the symbol cache is disabled."),
+ set_symbol_cache_size_handler, NULL,
+ &maintenance_set_cmdlist,
+ &maintenance_show_cmdlist);
+
+ add_cmd ("symbol-cache", class_maintenance, maintenance_print_symbol_cache,
+ _("Dump the symbol cache for each program space."),
+ &maintenanceprintlist);
+
+ add_cmd ("symbol-cache-statistics", class_maintenance,
+ maintenance_print_symbol_cache_statistics,
+ _("Print symbol cache statistics for each program space."),
+ &maintenanceprintlist);
+
+ add_cmd ("flush-symbol-cache", class_maintenance,
+ maintenance_flush_symbol_cache,
+ _("Flush the symbol cache for each program space."),
+ &maintenancelist);
+
observer_attach_executable_changed (symtab_observer_executable_changed);
+ observer_attach_new_objfile (symtab_new_objfile_observer);
+ observer_attach_free_objfile (symtab_free_objfile_observer);
}