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, 9 insertions, 4 deletions

diff --git a/libexec/rtld-elf/i386/reloc.c b/libexec/rtld-elf/i386/reloc.c
index 360733a..aff70b0 100644
--- a/libexec/rtld-elf/i386/reloc.c
+++ b/libexec/rtld-elf/i386/reloc.c
@@ -114,6 +114,11 @@ reloc_non_plt(Obj_Entry *obj, Obj_Entry *obj_rtld)
 {
 	const Elf_Rel *rellim;
 	const Elf_Rel *rel;
+	SymCache *cache;
+
+	cache = (SymCache *)alloca(obj->nchains * sizeof(SymCache));
+	if (cache != NULL)
+	    memset(cache, 0, obj->nchains * sizeof(SymCache));
 
 	rellim = (const Elf_Rel *) ((caddr_t) obj->rel + obj->relsize);
 	for (rel = obj->rel;  rel < rellim;  rel++) {
@@ -130,7 +135,7 @@ reloc_non_plt(Obj_Entry *obj, Obj_Entry *obj_rtld)
 		    const Obj_Entry *defobj;
 
 		    def = find_symdef(ELF_R_SYM(rel->r_info), obj, &defobj,
-		      false);
+		      false, cache);
 		    if (def == NULL)
 			return -1;
 
@@ -149,7 +154,7 @@ reloc_non_plt(Obj_Entry *obj, Obj_Entry *obj_rtld)
 		    const Obj_Entry *defobj;
 
 		    def = find_symdef(ELF_R_SYM(rel->r_info), obj, &defobj,
-		      false);
+		      false, cache);
 		    if (def == NULL)
 			return -1;
 
@@ -179,7 +184,7 @@ reloc_non_plt(Obj_Entry *obj, Obj_Entry *obj_rtld)
 		    const Obj_Entry *defobj;
 
 		    def = find_symdef(ELF_R_SYM(rel->r_info), obj, &defobj,
-		      false);
+		      false, cache);
 		    if (def == NULL)
 			return -1;
 
@@ -238,7 +243,7 @@ reloc_jmpslots(Obj_Entry *obj)
 
 	assert(ELF_R_TYPE(rel->r_info) == R_386_JMP_SLOT);
 	where = (Elf_Addr *)(obj->relocbase + rel->r_offset);
-	def = find_symdef(ELF_R_SYM(rel->r_info), obj, &defobj, true);
+	def = find_symdef(ELF_R_SYM(rel->r_info), obj, &defobj, true, NULL);
 	if (def == NULL)
 	    return -1;
 	reloc_jmpslot(where, (Elf_Addr)(defobj->relocbase + def->st_value));