From 54d68f2f4f2f10bb9939f8f532615295bf52ce96 Mon Sep 17 00:00:00 2001 From: Yinan Liu Date: Sat, 11 Sep 2021 21:50:43 +0800 Subject: [PATCH] scripts: ftrace - move the nop-processing in ftrace_init to compile time When ftrace is enabled, ftrace_init will consume a period of time, usually around 15~20ms. Approximately 60% of the time is consumed by nop-processing. Moving the nop-processing to the compile time can speed up the kernel boot process. performance test: env: Intel(R) Xeon(R) CPU E5-2682 v4 @ 2.50GHz method: before and after patching, compare the total time of ftrace_init(), and verify the functionality of ftrace. avg_time of ftrace_init: with patch: 7.114ms without patch: 15.763ms Signed-off-by: Yinan Liu --- kernel/trace/ftrace.c | 4 ++++ scripts/recordmcount.h | 14 ++++++++++++++ 2 files changed, 18 insertions(+) diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c index f1a4edbf0983b8..8226295e5d9849 100644 --- a/kernel/trace/ftrace.c +++ b/kernel/trace/ftrace.c @@ -6261,6 +6261,10 @@ static int ftrace_process_locs(struct module *mod, * until we are finished with it, and there's no * reason to cause large interrupt latencies while we do it. */ +#if defined CONFIG_X86 || defined CONFIG_X86_64 || defined CONFIG_ARM || defined CONFIG_ARM64 + ret = 0; + goto out; +#endif if (!mod) local_irq_save(flags); ftrace_update_code(mod, start_pg); diff --git a/scripts/recordmcount.h b/scripts/recordmcount.h index 1e9baa5c4fc6ef..152311639a0b33 100644 --- a/scripts/recordmcount.h +++ b/scripts/recordmcount.h @@ -406,6 +406,8 @@ static uint_t *sift_rel_mcount(uint_t *mlocp, uint_t const recval, unsigned const reltype) { + Elf_Shdr *const shdr0 = (Elf_Shdr *)(_w(ehdr->e_shoff) + (void *)ehdr); + Elf_Shdr const *const shdr = &shdr0[w(relhdr->sh_info)]; uint_t *const mloc0 = mlocp; Elf_Rel *mrelp = *mrelpp; Elf_Sym const *sym0; @@ -419,6 +421,7 @@ static uint_t *sift_rel_mcount(uint_t *mlocp, get_sym_str_and_relp(relhdr, ehdr, &sym0, &str0, &relp); for (t = nrel; t; --t) { + int ret = -1; if (!mcountsym) mcountsym = get_mcountsym(sym0, relp, str0); @@ -436,6 +439,17 @@ static uint_t *sift_rel_mcount(uint_t *mlocp, *mlocp++ = addend; mrelp = (Elf_Rel *)(rel_entsize + (void *)mrelp); + /* convert mcount into nop */ + if (make_nop) + ret = make_nop((void *)ehdr, + _w(shdr->sh_offset) + _w(relp->r_offset)); + if (!ret) { + Elf_Rel rel; + rel = *(Elf_Rel *)relp; + Elf_r_info(&rel, Elf_r_sym(relp), rel_type_nop); + ulseek(fd_map, (void *)relp - (void *)ehdr, SEEK_SET); + uwrite(fd_map, &rel, sizeof(rel)); + } } relp = (Elf_Rel const *)(rel_entsize + (void *)relp); }