Hi Peter, 2014-11-07 (금), 09:27 +0100, Peter Zijlstra: > On Fri, Nov 07, 2014 at 02:20:04PM +0900, Namhyung Kim wrote: > > When libelf is not used, perf cannot not show symbol names since it > > doesn't access the ELF symbol table. But kernel is different as it > > can fallback to kallsyms. > > > > It worked w/o libelf, but recent change to use vmlinux for kernel > > symbols break it. > > > > With this change, it now can show kernel symbols again: > > > > # Overhead Command Shared Object Symbol > > # ........ ....... ................. ........................ > > # > > 34.51% swapper [kernel.kallsyms] [k] intel_idle > > 12.54% perf [kernel.kallsyms] [k] generic_exec_single > > 10.11% swapper [kernel.kallsyms] [k] int_sqrt > > 9.83% swapper [kernel.kallsyms] [k] hrtimer_interrupt > > 7.25% emacs [kernel.kallsyms] [k] __switch_to > > 7.06% sleep [kernel.kallsyms] [k] find_next_iomem_res > > 7.02% swapper [kernel.kallsyms] [k] run_timer_softirq > > 2.55% swapper [kernel.kallsyms] [k] _raw_spin_unlock_irq > > 1.90% swapper [kernel.kallsyms] [k] lapic_next_deadline > > 1.75% swapper [kernel.kallsyms] [k] native_sched_clock > > 1.49% swapper [kernel.kallsyms] [k] __schedule > > 1.20% swapper [kernel.kallsyms] [k] read_tsc > > 1.10% sleep [kernel.kallsyms] [k] current_kernel_time > > 0.99% swapper [kernel.kallsyms] [k] pick_next_task_rt > > 0.36% swapper [kernel.kallsyms] [k] group_sched_in > > 0.24% swapper [kernel.kallsyms] [k] x86_pmu_commit_txn > > 0.06% swapper [kernel.kallsyms] [k] intel_pmu_enable_all > > 0.03% perf [kernel.kallsyms] [k] intel_pmu_enable_all > > > > Reported-by: Peter Zijlstra <a.p.zijls...@chello.nl> > > Cc: Adrian Hunter <adrian.hun...@intel.com> > > Signed-off-by: Namhyung Kim <namhy...@kernel.org> > > --- > > tools/perf/util/symbol-minimal.c | 3 +++ > > 1 file changed, 3 insertions(+) > > > > diff --git a/tools/perf/util/symbol-minimal.c > > b/tools/perf/util/symbol-minimal.c > > index c9541fea9514..226cf41ed7e6 100644 > > --- a/tools/perf/util/symbol-minimal.c > > +++ b/tools/perf/util/symbol-minimal.c > > @@ -335,6 +335,9 @@ int dso__load_sym(struct dso *dso, struct map *map > > __maybe_unused, > > unsigned char *build_id[BUILD_ID_SIZE]; > > int ret; > > > > + if (dso->kernel) > > + return 0; /* always use kallsyms */ > > + > > ret = fd__is_64_bit(ss->fd); > > if (ret >= 0) > > dso->is_64_bit = ret; > > Why does this live in the minimal implementation; should we not always > discard ELF files with 0 symbols? > > Suppose I have a vmlinux but removed all symbols from it; I want it to > fall back to kallsyms too.
I'm not sure I understood what you said correctly. With this change, dso__load_kernel_sym() always ends up calling dso__load_kallsyms() since dso__load_vmlinux() will always return 0; So I think you'll fall back to kallsyms even though you have a vmlinux with symbol. This makes dso__load_sym() in the patch 2/3 simpler IMHO. Thanks, Namhyung -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
