Messages in this thread Patch in this message | | | Date | Thu, 12 Mar 2020 14:41:19 +0100 | From | Peter Zijlstra <> | Subject | [RFC][PATCH 12/16] objtool: Optimize read_sections() |
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Perf showed that __hash_init() is a significant portion of read_sections(), so instead of doing a per section rela_hash, use an elf-wide rela_hash.
Statistics show us there are about 1.1 million relas, so size it accordingly.
This reduces the objtool on vmlinux.o runtime to a third, from 15 to 5 seconds.
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> --- tools/objtool/elf.c | 18 ++++++++++++------ tools/objtool/elf.h | 18 +++++++++++++++++- tools/objtool/orc_gen.c | 3 ++- 3 files changed, 31 insertions(+), 8 deletions(-)
--- a/tools/objtool/elf.c +++ b/tools/objtool/elf.c @@ -210,10 +210,15 @@ struct rela *find_rela_by_dest_range(str if (!sec->rela) return NULL; - for (o = offset; o < offset + len; o++) - hash_for_each_possible(sec->rela->rela_hash, rela, hash, o) - if (rela->offset == o) + sec = sec->rela; + + for (o = offset; o < offset + len; o++) { + hash_for_each_possible(sec->elf->rela_hash, rela, hash, + __rela_hash(o, sec->idx)) { + if (rela->sec == sec && rela->offset == o) return rela; + } + } return NULL; } @@ -248,9 +253,9 @@ static int read_sections(struct elf *elf } memset(sec, 0, sizeof(*sec)); + sec->elf = elf; INIT_LIST_HEAD(&sec->symbol_list); INIT_LIST_HEAD(&sec->rela_list); - hash_init(sec->rela_hash); list_add_tail(&sec->list, &elf->sections); @@ -485,7 +490,7 @@ static int read_relas(struct elf *elf) } list_add_tail(&rela->list, &sec->rela_list); - hash_add(sec->rela_hash, &rela->hash, rela->offset); + hash_add(elf->rela_hash, &rela->hash, rela_hash(rela)); nr_rela++; } max_rela = max(max_rela, nr_rela); @@ -518,6 +523,7 @@ struct elf *elf_read(const char *name, i 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->fd = open(name, flags); @@ -576,9 +582,9 @@ struct section *elf_create_section(struc } memset(sec, 0, sizeof(*sec)); + sec->elf = elf; INIT_LIST_HEAD(&sec->symbol_list); INIT_LIST_HEAD(&sec->rela_list); - hash_init(sec->rela_hash); list_add_tail(&sec->list, &elf->sections); --- a/tools/objtool/elf.h +++ b/tools/objtool/elf.h @@ -25,6 +25,8 @@ #define ELF_C_READ_MMAP ELF_C_READ #endif +struct elf; + struct section { struct list_head list; struct hlist_node hash; @@ -33,7 +35,7 @@ struct section { struct rb_root symbol_tree; struct list_head symbol_list; struct list_head rela_list; - DECLARE_HASHTABLE(rela_hash, 16); + struct elf *elf; struct section *base, *rela; struct symbol *sym; Elf_Data *data; @@ -81,8 +83,22 @@ struct elf { DECLARE_HASHTABLE(symbol_name_hash, 20); DECLARE_HASHTABLE(section_hash, 16); DECLARE_HASHTABLE(section_name_hash, 16); + DECLARE_HASHTABLE(rela_hash, 20); }; +static inline u32 __rela_hash(unsigned long offset, int idx) +{ + u32 ol = offset, oh = offset >> 32; + + __jhash_mix(ol, oh, idx); + + return ol; +} + +static inline u32 rela_hash(struct rela *rela) +{ + return __rela_hash(rela->offset, rela->sec->idx); +} struct elf *elf_read(const char *name, int flags); struct section *find_section_by_name(struct elf *elf, const char *name); --- a/tools/objtool/orc_gen.c +++ b/tools/objtool/orc_gen.c @@ -109,9 +109,10 @@ static int create_orc_entry(struct secti rela->addend = insn_off; rela->type = R_X86_64_PC32; rela->offset = idx * sizeof(int); + rela->sec = ip_relasec; list_add_tail(&rela->list, &ip_relasec->rela_list); - hash_add(ip_relasec->rela_hash, &rela->hash, rela->offset); + hash_add(ip_relasec->elf->rela_hash, &rela->hash, rela_hash(rela)); return 0; }
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