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    SubjectRe: [PATCH v4 02/53] perf record: Lazy load kernel symbols
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    On 2/11/23 19:56, 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@google.com>

    Reviewed-by: Adrian Hunter <adrian.hunter@intel.com>

    > ---
    > tools/perf/builtin-inject.c | 6 ++++++
    > tools/perf/builtin-record.c | 2 ++
    > tools/perf/util/event.c | 4 ++--
    > tools/perf/util/symbol_conf.h | 3 ++-
    > 4 files changed, 12 insertions(+), 3 deletions(-)
    >
    > diff --git a/tools/perf/builtin-inject.c b/tools/perf/builtin-inject.c
    > index c8cf2fdd9cff..eb3ef5c24b66 100644
    > --- a/tools/perf/builtin-inject.c
    > +++ b/tools/perf/builtin-inject.c
    > @@ -2265,6 +2265,12 @@ int cmd_inject(int argc, const char **argv)
    > "perf inject [<options>]",
    > NULL
    > };
    > +
    > + if (!inject.itrace_synth_opts.set) {
    > + /* Disable eager loading of kernel symbols that adds overhead to perf inject. */
    > + 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,

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