From: Anton Blanchard <anton@samba.org>
To: acme@redhat.com, a.p.zijlstra@chello.nl, paulus@samba.org,
mingo@redhat.com
Cc: linux-kernel@vger.kernel.org
Subject: [PATCH] perf: Ignore stripped vmlinux and fallback to kallsyms
Date: Tue, 9 Sep 2014 08:59:29 +1000 [thread overview]
Message-ID: <20140909085929.4a5a81f0@kryten> (raw)
If a vmlinux is stripped, perf will use it and ignore kallsyms. We
end up with useless profiles where everything maps to a few
runtime symbols:
63.39% swapper [kernel.kallsyms] [k] hcall_real_table
4.90% beam.smp [kernel.kallsyms] [k] hcall_real_table
4.44% beam.smp [kernel.kallsyms] [k] __sched_text_start
3.72% beam.smp [kernel.kallsyms] [k] __run_at_kexec
Detect this case and fallback to using kallsyms. This fixes the issue:
62.81% swapper [kernel.kallsyms] [k] snooze_loop
4.44% beam.smp [kernel.kallsyms] [k] __schedule
0.91% beam.smp [kernel.kallsyms] [k] _switch
0.73% beam.smp [kernel.kallsyms] [k] put_prev_entity
Signed-off-by: Anton Blanchard <anton@samba.org>
---
Index: b/tools/perf/util/symbol-elf.c
===================================================================
--- a/tools/perf/util/symbol-elf.c
+++ b/tools/perf/util/symbol-elf.c
@@ -712,6 +712,14 @@ int dso__load_sym(struct dso *dso, struc
symbols__delete(&dso->symbols[map->type]);
if (!syms_ss->symtab) {
+ /*
+ * If the vmlinux is stripped, fail so we will fall back
+ * to using kallsyms. The vmlinux runtime symbols aren't
+ * of much use.
+ */
+ if (dso->kernel)
+ goto out_elf_end;
+
syms_ss->symtab = syms_ss->dynsym;
syms_ss->symshdr = syms_ss->dynshdr;
}
next reply other threads:[~2014-09-08 22:59 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-09-08 22:59 Anton Blanchard [this message]
2014-09-12 6:33 ` [PATCH] perf: Ignore stripped vmlinux and fallback to kallsyms Namhyung Kim
2014-09-19 5:22 ` [tip:perf/core] perf symbols: " tip-bot for Anton Blanchard
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