On 15.12.2020 22:43, Jiri Olsa wrote: > On Tue, Dec 15, 2020 at 06:40:26PM +0300, Alexei Budankov wrote: >> Hi, >> >> On 12.12.2020 13:43, Jiri Olsa wrote: >>> Adding daemon command that allows to run record sessions >>> on background. Each session represents one perf record >>> process and is configured in config file. >>> >>> Example: >>> >>> # cat config.daemon >>> [daemon] >>> base=/opt/perfdata >> >> It could probably make sense to consider using locations at /var/ >> directory, similar to other already existing daemon processes in >> system so admin and user experience would be easily reusabe for >> performance monitoring daemon (service). > > hm, you can specify any /var path in there if you like, > do you suggest to hardcode it?
This thing: https://en.wikipedia.org/wiki/Filesystem_Hierarchy_Standard Since Perf is a part of OS it would better use some standardized locations. > >> >>> >>> [session-1] >>> run = -m 10M -e cycles -o /opt/perfdata/1/perf.data --overwrite >>> --switch-output -a >>> >>> [session-2] >>> run = -m 20M -e sched:* -o /opt/perfdata/2/perf.data --overwrite >>> --switch-output -a >>> >>> Default perf config has the same daemon base: >>> >>> # cat ~/.perfconfig >>> [daemon] >>> base=/opt/perfdata >>> >>> Starting the daemon: >>> >>> # perf daemon --config config.daemon >> >> It could make sense to name daemon config file similar to .perfconfig >> e.g. like .perfconfig.daemon. perf daemon command would then assume, by >> default, usage of .perfconfig.daemon config or the one specified on the >> command line via --config option. It also would be helpfull have loaded >> config file path printed into console: >> # perf daemon >> Daemon process <pid> started with config /path/to/.perfconfig.daemon > > so the current way is, that following creates daemon: > > # perf daemon --config <CONFIG> > > and any other 'non --config' option' is used to 'query/control' daemon: > > # perf daemon > # perf daemon --signal > # perf daemon --stop > ... > > > I'd like to keep short way checking on daemon, without too many > options, like: > > # perf daemon > [690174:daemon] base: /opt/perfdata > [690175:top] perf record -e cycles --switch-output=1m --switch-max-files=6 > -a > > > I think maybe we don't need any other .perfconfig, we could have > all in standard .perfconfig, like: > > # cat .perfconfig: > [daemon] > base=/opt/perfdata > > [session-1] > run = -m 1M -e cycles --overwrite --switch-output -a > [session-2] > run = -m 1M -e sched:* --overwrite --switch-output -a > > > and to run daemon on top of it: > > # perf daemon --start > > > to run daemon with alternate config: > > # perf daemon --start=<CONFIGFILE> > > or: > > # perf daemon --start --config=<CONFIGFILE> > > > and checking on daemon with default .perfconfig setup: > > # perf daemon > > > checking on daemon with different base or config: > > # perf daemon --base=<BASE> > # perf daemon --config=<CONFIGFILE> > # perf daemon --base=<BASE> --stop > # perf daemon --base=<BASE> --signal > # perf daemon --config=<CONFIGFILE> --stop > # perf daemon --config=<CONFIGFILE> --signal > > how about that? Extending .perfconfig would look simpler for users, IHMO. It looks like --base option actually implements --sandbox or similar semantics. > > SNIP > >>> +static struct session* >>> +daemon__find_session(struct daemon *daemon, char *name) >>> +{ >>> + struct session *session; >>> + >>> + list_for_each_entry(session, &daemon->sessions, list) { >>> + if (!strcmp(session->name, name)) >>> + return session; >>> + } >>> + >>> + return NULL; >>> +} >>> + >>> +static int session_name(const char *var, char *session, int len) >> >> should possibly name it get_session_name. > > ok > >> >>> +{ >>> + const char *p = var + sizeof("session-") - 1; >> >> should possibly check that p still points inside [var, var+len). > > ok > > SNIP > >>> +static int session__wait(struct session *session, struct daemon *daemon, >>> + int secs) >>> +{ >>> + time_t current, start = 0; >>> + int cnt; >>> + >>> + start = current = time(NULL); >>> + >>> + do { >>> + usleep(500); >> >> This polling design is actually sub-optimal because it induces redundant >> noise in a system. Ideally it should be implemented in async fashion so >> kernel would atomically notify daemon process on event happened in some >> of record processes e.g. using of poll-like() system call. > > ok, any suggestion? Possibly, checking SIGCHLDs via signalfd [1] OR using pidfd [2] on kernel v5.3+ [1] https://man7.org/linux/man-pages/man2/signalfd.2.html [2] https://man7.org/linux/man-pages/man2/pidfd_open.2.html Thanks, Alexei > >> >>> + cnt = session__check(session, daemon); >>> + if (cnt) >>> + break; >>> + >>> + current = time(NULL); >>> + } while ((start + secs > current)); >>> + >>> + return cnt; >>> +} >>> + >>> +static int session__signal(struct session *session, int sig) >>> +{ >>> + if (session->pid < 0) >>> + return -1; >>> + return kill(session->pid, sig); >> >> "Better" alternative could possibly be sending of some 'stop' command >> via --control=fd. > > true, nice idea.. seems more clean and we already have control fd open > > will add it to next version > > thanks, > jirka > > . >
