[tip: objtool/core] objtool: Optimize !vmlinux.o again
From: tip-bot2 for Peter Zijlstra
Date: Wed Apr 22 2020 - 18:26:23 EST
The following commit has been merged into the objtool/core branch of tip:
Commit-ID: 6700867cb19a52db07c4e9e86d51c6c8f01dcf8e
Gitweb: https://git.kernel.org/tip/6700867cb19a52db07c4e9e86d51c6c8f01dcf8e
Author: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
AuthorDate: Thu, 12 Mar 2020 14:29:38 +01:00
Committer: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
CommitterDate: Wed, 22 Apr 2020 23:10:07 +02:00
objtool: Optimize !vmlinux.o again
When doing kbuild tests to see if the objtool changes affected those I
found that there was a measurable regression:
pre post
real 1m13.594 1m16.488s
user 34m58.246s 35m23.947s
sys 4m0.393s 4m27.312s
Perf showed that for small files the increased hash-table sizes were a
measurable difference. Since we already have -l "vmlinux" to
distinguish between the modes, make it also use a smaller portion of
the hash-tables.
This flips it into a small win:
real 1m14.143s
user 34m49.292s
sys 3m44.746s
Signed-off-by: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx>
Reviewed-by: Miroslav Benes <mbenes@xxxxxxx>
Reviewed-by: Alexandre Chartre <alexandre.chartre@xxxxxxxxxx>
Acked-by: Josh Poimboeuf <jpoimboe@xxxxxxxxxx>
Link: https://lkml.kernel.org/r/20200416115119.167588731@xxxxxxxxxxxxx
---
tools/objtool/elf.c | 62 +++++++++++++++++++++++++++-------------
tools/objtool/elf.h | 13 ++++----
tools/objtool/orc_gen.c | 3 +--
3 files changed, 52 insertions(+), 26 deletions(-)
diff --git a/tools/objtool/elf.c b/tools/objtool/elf.c
index 03e542d..d384b9e 100644
--- a/tools/objtool/elf.c
+++ b/tools/objtool/elf.c
@@ -27,6 +27,22 @@ static inline u32 str_hash(const char *str)
return jhash(str, strlen(str), 0);
}
+static inline int elf_hash_bits(void)
+{
+ return vmlinux ? ELF_HASH_BITS : 16;
+}
+
+#define elf_hash_add(hashtable, node, key) \
+ hlist_add_head(node, &hashtable[hash_min(key, elf_hash_bits())])
+
+static void elf_hash_init(struct hlist_head *table)
+{
+ __hash_init(table, 1U << elf_hash_bits());
+}
+
+#define elf_hash_for_each_possible(name, obj, member, key) \
+ hlist_for_each_entry(obj, &name[hash_min(key, elf_hash_bits())], member)
+
static void rb_add(struct rb_root *tree, struct rb_node *node,
int (*cmp)(struct rb_node *, const struct rb_node *))
{
@@ -115,7 +131,7 @@ struct section *find_section_by_name(struct elf *elf, const char *name)
{
struct section *sec;
- hash_for_each_possible(elf->section_name_hash, sec, name_hash, str_hash(name))
+ elf_hash_for_each_possible(elf->section_name_hash, sec, name_hash, str_hash(name))
if (!strcmp(sec->name, name))
return sec;
@@ -127,7 +143,7 @@ static struct section *find_section_by_index(struct elf *elf,
{
struct section *sec;
- hash_for_each_possible(elf->section_hash, sec, hash, idx)
+ elf_hash_for_each_possible(elf->section_hash, sec, hash, idx)
if (sec->idx == idx)
return sec;
@@ -138,7 +154,7 @@ static struct symbol *find_symbol_by_index(struct elf *elf, unsigned int idx)
{
struct symbol *sym;
- hash_for_each_possible(elf->symbol_hash, sym, hash, idx)
+ elf_hash_for_each_possible(elf->symbol_hash, sym, hash, idx)
if (sym->idx == idx)
return sym;
@@ -205,7 +221,7 @@ struct symbol *find_symbol_by_name(struct elf *elf, const char *name)
{
struct symbol *sym;
- hash_for_each_possible(elf->symbol_name_hash, sym, name_hash, str_hash(name))
+ elf_hash_for_each_possible(elf->symbol_name_hash, sym, name_hash, str_hash(name))
if (!strcmp(sym->name, name))
return sym;
@@ -224,7 +240,7 @@ struct rela *find_rela_by_dest_range(struct elf *elf, struct section *sec,
sec = sec->rela;
for_offset_range(o, offset, offset + len) {
- hash_for_each_possible(elf->rela_hash, rela, hash,
+ elf_hash_for_each_possible(elf->rela_hash, rela, hash,
sec_offset_hash(sec, o)) {
if (rela->sec != sec)
continue;
@@ -309,8 +325,8 @@ static int read_sections(struct elf *elf)
sec->len = sec->sh.sh_size;
list_add_tail(&sec->list, &elf->sections);
- hash_add(elf->section_hash, &sec->hash, sec->idx);
- hash_add(elf->section_name_hash, &sec->name_hash, str_hash(sec->name));
+ elf_hash_add(elf->section_hash, &sec->hash, sec->idx);
+ elf_hash_add(elf->section_name_hash, &sec->name_hash, str_hash(sec->name));
}
if (stats)
@@ -404,8 +420,8 @@ static int read_symbols(struct elf *elf)
else
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));
+ elf_hash_add(elf->symbol_hash, &sym->hash, sym->idx);
+ elf_hash_add(elf->symbol_name_hash, &sym->name_hash, str_hash(sym->name));
}
if (stats)
@@ -472,6 +488,14 @@ err:
return -1;
}
+void elf_add_rela(struct elf *elf, struct rela *rela)
+{
+ struct section *sec = rela->sec;
+
+ list_add_tail(&rela->list, &sec->rela_list);
+ elf_hash_add(elf->rela_hash, &rela->hash, rela_hash(rela));
+}
+
static int read_relas(struct elf *elf)
{
struct section *sec;
@@ -519,8 +543,7 @@ static int read_relas(struct elf *elf)
return -1;
}
- list_add_tail(&rela->list, &sec->rela_list);
- hash_add(elf->rela_hash, &rela->hash, rela_hash(rela));
+ elf_add_rela(elf, rela);
nr_rela++;
}
max_rela = max(max_rela, nr_rela);
@@ -547,15 +570,16 @@ struct elf *elf_read(const char *name, int flags)
perror("malloc");
return NULL;
}
- memset(elf, 0, sizeof(*elf));
+ memset(elf, 0, offsetof(struct elf, sections));
- hash_init(elf->symbol_hash);
- hash_init(elf->symbol_name_hash);
- hash_init(elf->section_hash);
- hash_init(elf->section_name_hash);
- hash_init(elf->rela_hash);
INIT_LIST_HEAD(&elf->sections);
+ elf_hash_init(elf->symbol_hash);
+ elf_hash_init(elf->symbol_name_hash);
+ elf_hash_init(elf->section_hash);
+ elf_hash_init(elf->section_name_hash);
+ elf_hash_init(elf->rela_hash);
+
elf->fd = open(name, flags);
if (elf->fd == -1) {
fprintf(stderr, "objtool: Can't open '%s': %s\n",
@@ -692,8 +716,8 @@ struct section *elf_create_section(struct elf *elf, const char *name,
shstrtab->changed = true;
list_add_tail(&sec->list, &elf->sections);
- hash_add(elf->section_hash, &sec->hash, sec->idx);
- hash_add(elf->section_name_hash, &sec->name_hash, str_hash(sec->name));
+ elf_hash_add(elf->section_hash, &sec->hash, sec->idx);
+ elf_hash_add(elf->section_name_hash, &sec->name_hash, str_hash(sec->name));
return sec;
}
diff --git a/tools/objtool/elf.h b/tools/objtool/elf.h
index eb79cb9..2811d04 100644
--- a/tools/objtool/elf.h
+++ b/tools/objtool/elf.h
@@ -70,17 +70,19 @@ struct rela {
bool jump_table_start;
};
+#define ELF_HASH_BITS 20
+
struct elf {
Elf *elf;
GElf_Ehdr ehdr;
int fd;
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);
- DECLARE_HASHTABLE(rela_hash, 20);
+ DECLARE_HASHTABLE(symbol_hash, ELF_HASH_BITS);
+ DECLARE_HASHTABLE(symbol_name_hash, ELF_HASH_BITS);
+ DECLARE_HASHTABLE(section_hash, ELF_HASH_BITS);
+ DECLARE_HASHTABLE(section_name_hash, ELF_HASH_BITS);
+ DECLARE_HASHTABLE(rela_hash, ELF_HASH_BITS);
};
#define OFFSET_STRIDE_BITS 4
@@ -127,6 +129,7 @@ struct section *elf_create_rela_section(struct elf *elf, struct section *base);
int elf_rebuild_rela_section(struct section *sec);
int elf_write(struct elf *elf);
void elf_close(struct elf *elf);
+void elf_add_rela(struct elf *elf, struct rela *rela);
#define for_each_sec(file, sec) \
list_for_each_entry(sec, &file->elf->sections, list)
diff --git a/tools/objtool/orc_gen.c b/tools/objtool/orc_gen.c
index 2cf640f..9d2bf2d 100644
--- a/tools/objtool/orc_gen.c
+++ b/tools/objtool/orc_gen.c
@@ -130,8 +130,7 @@ static int create_orc_entry(struct elf *elf, struct section *u_sec, struct secti
rela->offset = idx * sizeof(int);
rela->sec = ip_relasec;
- list_add_tail(&rela->list, &ip_relasec->rela_list);
- hash_add(elf->rela_hash, &rela->hash, rela_hash(rela));
+ elf_add_rela(elf, rela);
return 0;
}