lkml.org 
[lkml]   [2014]   [Nov]   [7]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [PATCH 1/3] perf tools: Allow vmlinux to fallback to kallsyms on NO_LIBELF=1
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.zijlstra@chello.nl>
> Cc: Adrian Hunter <adrian.hunter@intel.com>
> Signed-off-by: Namhyung Kim <namhyung@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.


\
 
 \ /
  Last update: 2014-11-07 10:01    [W:0.102 / U:1.588 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site