Messages in this thread Patch in this message | | | Date | Thu, 12 Mar 2020 14:41:23 +0100 | From | Peter Zijlstra <> | Subject | [RFC][PATCH 16/16] objtool: Optimize !vmlinux.o again |
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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@infradead.org> --- tools/objtool/elf.c | 40 ++++++++++++++++++++++++++++------------ tools/objtool/elf.h | 4 ++-- 2 files changed, 30 insertions(+), 14 deletions(-)
--- a/tools/objtool/elf.c +++ b/tools/objtool/elf.c @@ -27,6 +27,21 @@ static inline u32 str_hash(const char *s return jhash(str, strlen(str), 0); } +static inline int elf_hash_bits(void) +{ + return vmlinux ? 20 : 16; +} + +static inline void elf_hash_add(struct hlist_head *table, struct hlist_node *node, u32 key) +{ + hlist_add_head(node, &table[hash_32(key, elf_hash_bits())]); +} + +static void elf_hash_init(struct hlist_head *table) +{ + __hash_init(table, 1U << elf_hash_bits()); +} + static void rb_add(struct rb_root *tree, struct rb_node *node, int (*cmp)(struct rb_node *, const struct rb_node *)) { @@ -300,8 +315,8 @@ static int read_sections(struct elf *elf } sec->len = sec->sh.sh_size; - 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) @@ -387,8 +402,8 @@ 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)); + 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) @@ -497,7 +512,7 @@ static int read_relas(struct elf *elf) } list_add_tail(&rela->list, &sec->rela_list); - hash_add(elf->rela_hash, &rela->hash, rela_hash(rela)); + elf_hash_add(elf->rela_hash, &rela->hash, rela_hash(rela)); nr_rela++; } max_rela = max(max_rela, nr_rela); @@ -524,15 +539,16 @@ struct elf *elf_read(const char *name, i 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", @@ -671,7 +687,7 @@ struct section *elf_create_section(struc shstrtab->len += strlen(name) + 1; shstrtab->changed = true; - hash_add(elf->section_hash, &sec->hash, sec->idx); + elf_hash_add(elf->section_hash, &sec->hash, sec->idx); return sec; } --- a/tools/objtool/elf.h +++ b/tools/objtool/elf.h @@ -81,8 +81,8 @@ struct elf { 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(section_hash, 20); + DECLARE_HASHTABLE(section_name_hash, 20); DECLARE_HASHTABLE(rela_hash, 20); };
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