Re: [PATCH 06/24] perf daemon: Add config file support

From: Arnaldo Carvalho de Melo <acme@kernel.org>
To: Jiri Olsa <jolsa@redhat.com>
Cc: Namhyung Kim <namhyung@kernel.org>, Jiri Olsa <jolsa@kernel.org>,
	lkml <linux-kernel@vger.kernel.org>,
	Peter Zijlstra <a.p.zijlstra@chello.nl>,
	Ingo Molnar <mingo@kernel.org>,
	Mark Rutland <mark.rutland@arm.com>,
	Alexander Shishkin <alexander.shishkin@linux.intel.com>,
	Michael Petlan <mpetlan@redhat.com>,
	Ian Rogers <irogers@google.com>,
	Alexei Budankov <abudankov@huawei.com>
Subject: Re: [PATCH 06/24] perf daemon: Add config file support
Date: Thu, 11 Feb 2021 14:10:48 -0300	[thread overview]
Message-ID: <20210211171048.GF1131885@kernel.org> (raw)
In-Reply-To: <YCVfMmYmPTm2r6ct@krava>

Em Thu, Feb 11, 2021 at 05:45:38PM +0100, Jiri Olsa escreveu:
> On Thu, Feb 11, 2021 at 03:01:12PM +0900, Namhyung Kim wrote:
> > Hi Jiri,
> > 
> > On Tue, Feb 9, 2021 at 5:09 AM Jiri Olsa <jolsa@kernel.org> wrote:
> > > +static int daemon__reconfig(struct daemon *daemon)
> > > +{
> > > +       struct daemon_session *session, *n;
> > > +
> > > +       list_for_each_entry_safe(session, n, &daemon->sessions, list) {
> > > +               /* No change. */
> > > +               if (session->state == OK)
> > > +                       continue;
> > > +
> > > +               /* Remove session. */
> > > +               if (session->state == KILL) {
> > > +                       if (session->pid > 0) {
> > > +                               daemon_session__kill(session);
> > > +                               pr_info("reconfig: session '%s' killed\n", session->name);
> > > +                       }
> > > +                       daemon_session__remove(session);
> > > +                       continue;
> > > +               }
> > > +
> > > +               /* Reconfig session. */
> > > +               if (session->pid > 0) {
> > > +                       daemon_session__kill(session);
> > > +                       pr_info("reconfig: session '%s' killed\n", session->name);
> > > +               }
> > > +               if (daemon_session__run(session, daemon))
> > > +                       return -1;
> > 
> > Shouldn't it be 'continue'?  If there's a problematic session
> > it'll prevent others from being processed.  And it seems this
> > code will try to run it again and again.  Maybe we can put it
> > in the KILL state (or a new FAILED state) IMHO.
> 
> so if there is misconfigured session, it will get executed,
> and then we catch that it exited, like:
> 
> 	# ./perf daemon start -f
> 	[2021-02-11 17:38:19.718166] daemon started (pid 1167439)
> 	[2021-02-11 17:38:19.719757] reconfig: ruining session [cycles:1167440]: abc -m 10M -e cycles --overwrite --switch-output -a
> 	[2021-02-11 17:38:19.720861] reconfig: ruining session [sched:1167441]: -m 20M -e sched:* --overwrite --switch-output -a
> 	[2021-02-11 17:38:21.132511] session 'cycles' exited, status=255
> 
> session will be removed
> 
> when the config is fixed and updated, daemon will pick it up:
> 
> 	[2021-02-11 17:42:59.241140] reconfig: ruining session [cycles:1167642]: -m 10M -e cycles --overwrite --switch-output -a
> 
> 
> daemon_session__run fails only there's no memory for allocation,
> if mkdir fails (for other error than EEXIST) and if fork fails,
> so pretty serious errors, where we want to bail out anyway

I know you love documentation, that is why I think that it would be a
good idea to have these questions and answers in a FAQ for 'perf
daemon', don't you think? ;-)

- Arnaldo