From 91c17d33324b51a3876bc6ce778c684111139303 Mon Sep 17 00:00:00 2001
From: Chris Wilson <chris@chris-wilson.co.uk>
Date: Tue, 18 Nov 2008 00:32:54 +0000
Subject: [PATCH] [trace] Simple unbounded cache for symbol lookups.

Reparsing the dwarf info for every lookup is very slow, so cache the
symbol lookups. This initial implementation is unbounded in the simple
belief that the actual number of unique lookups during a program's
lifetime should be fairly small. (Extending to a bounded MRU list is left
as an exercise for the reader.)
---
 util/cairo-trace/lookup-symbol.c | 68 +++++++++++++++++++++++++++-----
 util/cairo-trace/trace.c         |  9 +++--
 2 files changed, 64 insertions(+), 13 deletions(-)

diff --git a/util/cairo-trace/lookup-symbol.c b/util/cairo-trace/lookup-symbol.c
index 42c9c9554..eb1a656dd 100644
--- a/util/cairo-trace/lookup-symbol.c
+++ b/util/cairo-trace/lookup-symbol.c
@@ -61,6 +61,7 @@
 #include <stdlib.h>
 #include <link.h>
 #include <string.h>
+#include <pthread.h>
 
 #if HAVE_BFD
 #include <bfd.h>
@@ -246,6 +247,15 @@ find_matching_file (struct dl_phdr_info *info, size_t size, void *data)
     return 0;
 }
 
+struct symbol_cache_entry {
+    const void *ptr;
+    struct symbol_cache_entry *hash_prev, *hash_next;
+    char name[0];
+};
+
+static struct symbol_cache_entry *symbol_cache_hash[13477];
+static pthread_mutex_t symbol_cache_mutex = PTHREAD_MUTEX_INITIALIZER;
+
 char *
 lookup_symbol (char *buf, int buflen, const void *ptr)
 {
@@ -254,6 +264,32 @@ lookup_symbol (char *buf, int buflen, const void *ptr)
     struct symtab symtab;
     struct symbol symbol;
 #endif
+    struct symbol_cache_entry *cache;
+    int bucket;
+    int len;
+
+    bucket = (unsigned long) ptr % (sizeof (symbol_cache_hash) / sizeof (symbol_cache_hash[0]));
+    pthread_mutex_lock (&symbol_cache_mutex);
+    for (cache = symbol_cache_hash[bucket];
+	 cache != NULL;
+	 cache = cache->hash_next)
+    {
+	if (cache->ptr == ptr) {
+	    if (cache->hash_prev != NULL) {
+		cache->hash_prev->hash_next = cache->hash_next;
+		if (cache->hash_next != NULL)
+		    cache->hash_next->hash_prev = cache->hash_prev;
+		cache->hash_prev = NULL;
+		cache->hash_next = symbol_cache_hash[bucket];
+		symbol_cache_hash[bucket]->hash_prev = cache;
+		symbol_cache_hash[bucket] = cache;
+	    }
+
+	    pthread_mutex_unlock (&symbol_cache_mutex);
+	    return cache->name;
+	}
+    }
+    pthread_mutex_unlock (&symbol_cache_mutex);
 
     match.file = NULL;
     match.address = (ElfW(Addr)) ptr;
@@ -266,17 +302,31 @@ lookup_symbol (char *buf, int buflen, const void *ptr)
 	match.file = "/proc/self/exe";
 
 #if HAVE_BFD
-    if (! _symtab_init (&symtab, match.file))
-	return buf;
+    if (_symtab_init (&symtab, match.file)) {
+	_symbol_init (&symbol, &symtab, match.address - match.base);
+	bfd_map_over_sections (symtab.bfd, find_address_in_section, &symbol);
+	if (symbol.found)
+	    _symbol_print (&symbol, buf, buflen, match.file);
+	_symbol_fini (&symbol);
 
-    _symbol_init (&symbol, &symtab, match.address - match.base);
-    bfd_map_over_sections (symtab.bfd, find_address_in_section, &symbol);
-    if (symbol.found)
-	_symbol_print (&symbol, buf, buflen, match.file);
-    _symbol_fini (&symbol);
-
-    _symtab_fini (&symtab);
+	_symtab_fini (&symtab);
+    }
 #endif
 
+    len = strlen (buf);
+    cache = malloc (sizeof (struct symbol_cache_entry) + len + 1);
+    if (cache != NULL) {
+	cache->ptr = ptr;
+	memcpy (cache->name, buf, len + 1);
+
+	pthread_mutex_lock (&symbol_cache_mutex);
+	cache->hash_prev = NULL;
+	cache->hash_next = symbol_cache_hash[bucket];
+	if (symbol_cache_hash[bucket] != NULL)
+	    symbol_cache_hash[bucket]->hash_prev = cache;
+	symbol_cache_hash[bucket] = cache;
+	pthread_mutex_unlock (&symbol_cache_mutex);
+    }
+
     return buf;
 }
diff --git a/util/cairo-trace/trace.c b/util/cairo-trace/trace.c
index fb3a38ccf..1b94ea1e5 100644
--- a/util/cairo-trace/trace.c
+++ b/util/cairo-trace/trace.c
@@ -157,8 +157,8 @@ static const cairo_user_data_key_t destroy_key;
     if (_line_info && _write_lock ()) { \
 	void *addr = __builtin_return_address(0); \
 	char caller[1024]; \
-	lookup_symbol (caller, sizeof (caller), addr); \
-	fprintf (logfile, "%% %s() called by %s\n", __FUNCTION__, caller); \
+	fprintf (logfile, "%% %s() called by %s\n", __FUNCTION__, \
+		 lookup_symbol (caller, sizeof (caller), addr)); \
 	_write_unlock (); \
     } \
 } while (0)
@@ -2983,8 +2983,9 @@ cairo_surface_write_to_png_stream (cairo_surface_t *surface,
 	char symbol[1024];
 
 	fprintf (logfile, "%% s%ld ", _get_surface_id (surface));
-	lookup_symbol (symbol, sizeof (symbol), write_func);
-	_emit_string_literal (symbol, -1);
+	_emit_string_literal (lookup_symbol (symbol, sizeof (symbol),
+					     write_func),
+			      -1);
 	fprintf (logfile, " write_to_png_stream\n");
 	_write_unlock ();
     }