On 12/10/23 09:23, Ian Rogers wrote:
> Commit 5b7ba82a7591 ("perf symbols: Load kernel maps before using")
> changed it so that loading a kernel dso would cause the symbols for
> the dso to be eagerly loaded. For perf record this is overhead as the
> symbols won't be used. Add a symbol_conf to control the behavior and
> disable it for perf record and perf inject.
>
> Signed-off-by: Ian Rogers <irogers@xxxxxxxxxx>
> ---
> tools/perf/builtin-inject.c | 4 ++++
> tools/perf/builtin-record.c | 2 ++
> tools/perf/util/event.c | 4 ++--
> tools/perf/util/symbol_conf.h | 3 ++-
> 4 files changed, 10 insertions(+), 3 deletions(-)
>
> diff --git a/tools/perf/builtin-inject.c b/tools/perf/builtin-inject.c
> index c8cf2fdd9cff..1539fb18c749 100644
> --- a/tools/perf/builtin-inject.c
> +++ b/tools/perf/builtin-inject.c
> @@ -2265,6 +2265,10 @@ int cmd_inject(int argc, const char **argv)
> "perf inject [<options>]",
> NULL
> };
> +
> + /* Disable eager loading of kernel symbols that adds overhead to perf inject. */
> + symbol_conf.lazy_load_kernel_maps = true;
Possibly not for itrace kernel decoding, so:
if (!inject->itrace_synth_opts.set)
symbol_conf.lazy_load_kernel_maps = true;
> +
> #ifndef HAVE_JITDUMP
> set_option_nobuild(options, 'j', "jit", "NO_LIBELF=1", true);
> #endif
> diff --git a/tools/perf/builtin-record.c b/tools/perf/builtin-record.c
> index dcf288a4fb9a..8ec818568662 100644
> --- a/tools/perf/builtin-record.c
> +++ b/tools/perf/builtin-record.c
> @@ -3989,6 +3989,8 @@ int cmd_record(int argc, const char **argv)
> # undef set_nobuild
> #endif
>
> + /* Disable eager loading of kernel symbols that adds overhead to perf record. */
> + symbol_conf.lazy_load_kernel_maps = true;
> rec->opts.affinity = PERF_AFFINITY_SYS;
>
> rec->evlist = evlist__new();
> diff --git a/tools/perf/util/event.c b/tools/perf/util/event.c
> index 923c0fb15122..68f45e9e63b6 100644
> --- a/tools/perf/util/event.c
> +++ b/tools/perf/util/event.c
> @@ -617,13 +617,13 @@ struct map *thread__find_map(struct thread *thread, u8 cpumode, u64 addr,
> if (cpumode == PERF_RECORD_MISC_KERNEL && perf_host) {
> al->level = 'k';
> maps = machine__kernel_maps(machine);
> - load_map = true;
> + load_map = !symbol_conf.lazy_load_kernel_maps;
> } else if (cpumode == PERF_RECORD_MISC_USER && perf_host) {
> al->level = '.';
> } else if (cpumode == PERF_RECORD_MISC_GUEST_KERNEL && perf_guest) {
> al->level = 'g';
> maps = machine__kernel_maps(machine);
> - load_map = true;
> + load_map = !symbol_conf.lazy_load_kernel_maps;
> } else if (cpumode == PERF_RECORD_MISC_GUEST_USER && perf_guest) {
> al->level = 'u';
> } else {
> diff --git a/tools/perf/util/symbol_conf.h b/tools/perf/util/symbol_conf.h
> index 0b589570d1d0..2b2fb9e224b0 100644
> --- a/tools/perf/util/symbol_conf.h
> +++ b/tools/perf/util/symbol_conf.h
> @@ -42,7 +42,8 @@ struct symbol_conf {
> inline_name,
> disable_add2line_warn,
> buildid_mmap2,
> - guest_code;
> + guest_code,
> + lazy_load_kernel_maps;
> const char *vmlinux_name,
> *kallsyms_name,
> *source_prefix,
