objtool: Optimize find_symbol_by_name()

Perf showed that find_symbol_by_name() takes time; add a symbol name
hash.

This shaves another second off of objtool on vmlinux.o runtime, down
to 15 seconds.

Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Miroslav Benes <mbenes@suse.cz>
Acked-by: Josh Poimboeuf <jpoimboe@redhat.com>
Link: https://lkml.kernel.org/r/20200324160924.676865656@infradead.org

diff --git a/tools/objtool/elf.c b/tools/objtool/elf.c
index 07db4df..43abae7 100644 (file)
--- a/tools/objtool/elf.c
+++ b/tools/objtool/elf.c
@@ -203,13 +203,11 @@ struct symbol *find_func_containing(struct section *sec, unsigned long offset)
 
 struct symbol *find_symbol_by_name(struct elf *elf, const char *name)
 {
-       struct section *sec;
        struct symbol *sym;
 
-       list_for_each_entry(sec, &elf->sections, list)
-               list_for_each_entry(sym, &sec->symbol_list, list)
-                       if (!strcmp(sym->name, name))
-                               return sym;
+       hash_for_each_possible(elf->symbol_name_hash, sym, name_hash, str_hash(name))
+               if (!strcmp(sym->name, name))
+                       return sym;
 
        return NULL;
 }
@@ -386,6 +384,7 @@ static int read_symbols(struct elf *elf)
                        entry = &sym->sec->symbol_list;
                list_add(&sym->list, entry);
                hash_add(elf->symbol_hash, &sym->hash, sym->idx);
+               hash_add(elf->symbol_name_hash, &sym->name_hash, str_hash(sym->name));
        }
 
        if (stats)
@@ -524,6 +523,7 @@ struct elf *elf_read(const char *name, int flags)
        memset(elf, 0, sizeof(*elf));
 
        hash_init(elf->symbol_hash);
+       hash_init(elf->symbol_name_hash);
        hash_init(elf->section_hash);
        hash_init(elf->section_name_hash);
        INIT_LIST_HEAD(&elf->sections);

diff --git a/tools/objtool/elf.h b/tools/objtool/elf.h
index d18f466..3088d92 100644 (file)
--- a/tools/objtool/elf.h
+++ b/tools/objtool/elf.h
@@ -47,6 +47,7 @@ struct symbol {
        struct list_head list;
        struct rb_node node;
        struct hlist_node hash;
+       struct hlist_node name_hash;
        GElf_Sym sym;
        struct section *sec;
        char *name;
@@ -77,6 +78,7 @@ struct elf {
        char *name;
        struct list_head sections;
        DECLARE_HASHTABLE(symbol_hash, 20);
+       DECLARE_HASHTABLE(symbol_name_hash, 20);
        DECLARE_HASHTABLE(section_hash, 16);
        DECLARE_HASHTABLE(section_name_hash, 16);
 };