Performance improvements for the ELF dynamic linker. These

particularly help programs which load many shared libraries with
a lot of relocations.  Large C++ programs such as are found in KDE
are a prime example.

While relocating a shared object, maintain a vector of symbols
which have already been looked up, directly indexed by symbol
number.  Typically, symbols which are referenced by a relocation
entry are referenced by many of them.  This is the same optimization
I made to the a.out dynamic linker in 1995 (rtld.c revision 1.30).

Also, compare the first character of a sought-after symbol with its
symbol table entry before calling strcmp().

On a PII/400 these changes reduce the start-up time of a typical
KDE program from 833 msec (elapsed) to 370 msec.

MFC after:	5 days

1 files changed, 10 insertions, 1 deletions

diff --git a/libexec/rtld-elf/rtld.h b/libexec/rtld-elf/rtld.h
index 5ac7c12..3476826 100644
--- a/libexec/rtld-elf/rtld.h
+++ b/libexec/rtld-elf/rtld.h
@@ -166,6 +166,15 @@ typedef struct Struct_Obj_Entry {
 #define RTLD_MAGIC	0xd550b87a
 #define RTLD_VERSION	1
 
+/*
+ * Symbol cache entry used during relocation to avoid multiple lookups
+ * of the same symbol.
+ */
+typedef struct Struct_SymCache {
+    const Elf_Sym *sym;		/* Symbol table entry */
+    const Obj_Entry *obj;	/* Shared object which defines it */
+} SymCache;
+
 extern void _rtld_error(const char *, ...) __printflike(1, 2);
 extern Obj_Entry *map_object(int, const char *, const struct stat *);
 extern void *xcalloc(size_t);
@@ -179,7 +188,7 @@ extern Elf_Addr _GLOBAL_OFFSET_TABLE_[];
 int do_copy_relocations(Obj_Entry *);
 unsigned long elf_hash(const char *);
 const Elf_Sym *find_symdef(unsigned long, const Obj_Entry *,
-  const Obj_Entry **, bool);
+  const Obj_Entry **, bool, SymCache *);
 void init_pltgot(Obj_Entry *);
 void lockdflt_init(LockInfo *);
 void obj_free(Obj_Entry *);