From 74b873e49d92f90deb41d1a2a8fbb70328aebd67 Mon Sep 17 00:00:00 2001 From: Peter Zijlstra Date: Thu, 12 Mar 2020 11:30:50 +0100 Subject: [PATCH] objtool: Optimize find_rela_by_dest_range() Perf shows there is significant time in find_rela_by_dest(); this is because we have to iterate the address space per byte, looking for relocation entries. Optimize this by reducing the address space granularity. This reduces objtool on vmlinux.o runtime from 4.8 to 4.4 seconds. Signed-off-by: Peter Zijlstra (Intel) Reviewed-by: Miroslav Benes Acked-by: Josh Poimboeuf Link: https://lkml.kernel.org/r/20200324160924.861321325@infradead.org --- tools/objtool/elf.c | 15 +++++++++++---- tools/objtool/elf.h | 16 +++++++++++++++- 2 files changed, 26 insertions(+), 5 deletions(-) diff --git a/tools/objtool/elf.c b/tools/objtool/elf.c index 8a0a1bc..09ddc8f 100644 --- a/tools/objtool/elf.c +++ b/tools/objtool/elf.c @@ -215,7 +215,7 @@ struct symbol *find_symbol_by_name(struct elf *elf, const char *name) struct rela *find_rela_by_dest_range(struct elf *elf, struct section *sec, unsigned long offset, unsigned int len) { - struct rela *rela; + struct rela *rela, *r = NULL; unsigned long o; if (!sec->rela) @@ -223,12 +223,19 @@ struct rela *find_rela_by_dest_range(struct elf *elf, struct section *sec, sec = sec->rela; - for (o = offset; o < offset + len; o++) { + for_offset_range(o, offset, offset + len) { hash_for_each_possible(elf->rela_hash, rela, hash, sec_offset_hash(sec, o)) { - if (rela->sec == sec && rela->offset == o) - return rela; + if (rela->sec != sec) + continue; + + if (rela->offset >= offset && rela->offset < offset + len) { + if (!r || rela->offset < r->offset) + r = rela; + } } + if (r) + return r; } return NULL; diff --git a/tools/objtool/elf.h b/tools/objtool/elf.h index dfd2431..ebbb10c 100644 --- a/tools/objtool/elf.h +++ b/tools/objtool/elf.h @@ -83,9 +83,23 @@ struct elf { DECLARE_HASHTABLE(rela_hash, 20); }; +#define OFFSET_STRIDE_BITS 4 +#define OFFSET_STRIDE (1UL << OFFSET_STRIDE_BITS) +#define OFFSET_STRIDE_MASK (~(OFFSET_STRIDE - 1)) + +#define for_offset_range(_offset, _start, _end) \ + for (_offset = ((_start) & OFFSET_STRIDE_MASK); \ + _offset <= ((_end) & OFFSET_STRIDE_MASK); \ + _offset += OFFSET_STRIDE) + static inline u32 sec_offset_hash(struct section *sec, unsigned long offset) { - u32 ol = offset, oh = offset >> 32, idx = sec->idx; + u32 ol, oh, idx = sec->idx; + + offset &= OFFSET_STRIDE_MASK; + + ol = offset; + oh = offset >> 32; __jhash_mix(ol, oh, idx); -- 2.7.4