On Fri, May 1, 2020 at 5:23 AM Jiri Olsa <jo...@redhat.com> wrote: > > On Thu, Apr 30, 2020 at 12:35:57PM -0700, Ian Rogers wrote: > > Perf record will call kallsyms__parse 4 times during startup and process > > megabytes of data. This changes kallsyms__parse to use the io library > > rather than fgets to improve performance of the user code by over 8%. > > > > Before: > > Running 'internals/kallsyms-parse' benchmark: > > Average kallsyms__parse took: 103.988 ms (+- 0.203 ms) > > After: > > Running 'internals/kallsyms-parse' benchmark: > > Average kallsyms__parse took: 95.571 ms (+- 0.006 ms) > > > > For a workload like: > > $ perf record /bin/true > > Run under 'perf record -e cycles:u -g' the time goes from: > > Before > > 30.10% 1.67% perf perf [.] kallsyms__parse > > After > > 25.55% 20.04% perf perf [.] kallsyms__parse > > So a little under 5% of the start-up time is removed. A lot of what > > remains is on the kernel side, but caching kallsyms within perf would > > at least impact memory footprint. > > with your change I'm getting following warnings: > > $ sudo ./perf record -a > Couldn't record kernel reference relocation symbol > Symbol resolution may be skewed if relocation was used (e.g. kexec). > Check /proc/kallsyms permission or run as root.
I'll investigate, sorry in advance for sending this out too early. > > > > Signed-off-by: Ian Rogers <irog...@google.com> > > --- > > tools/lib/api/io.h | 3 ++ > > tools/lib/symbol/kallsyms.c | 81 +++++++++++++++++++------------------ > > 2 files changed, 44 insertions(+), 40 deletions(-) > > > > diff --git a/tools/lib/api/io.h b/tools/lib/api/io.h > > index b7e55b5f8a4a..777c20f6b604 100644 > > --- a/tools/lib/api/io.h > > +++ b/tools/lib/api/io.h > > @@ -7,6 +7,9 @@ > > #ifndef __API_IO__ > > #define __API_IO__ > > > > +#include <stdlib.h> > > +#include <unistd.h> > > was this missing? Yes, they were getting picked up by a transitive #include in synthesize-events.c, but given the call to read and use of size_t are here it makes sense for the #includes to be here. Thanks, Ian > jirka > > > + > > struct io { > > /* File descriptor being read/ */ > > int fd; > > SNIP >