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. > > 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? jirka > + > struct io { > /* File descriptor being read/ */ > int fd; SNIP