From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751717AbdGZQjD (ORCPT ); Wed, 26 Jul 2017 12:39:03 -0400 Received: from mga11.intel.com ([192.55.52.93]:24287 "EHLO mga11.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750893AbdGZQjC (ORCPT ); Wed, 26 Jul 2017 12:39:02 -0400 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.40,416,1496127600"; d="scan'208";a="1199588765" Message-ID: <1501087113.3214.11.camel@tzanussi-mobl.amr.corp.intel.com> Subject: Re: [PATCH 23/32] tracing: Add 'onmatch' hist trigger action support From: Tom Zanussi To: Namhyung Kim Cc: rostedt@goodmis.org, tglx@linutronix.de, mhiramat@kernel.org, vedang.patel@intel.com, linux-kernel@vger.kernel.org, linux-rt-users@vger.kernel.org, kernel-team@lge.com Date: Wed, 26 Jul 2017 11:38:33 -0500 In-Reply-To: <20170726024019.GA32043@sejong> References: <8411497118160688b13fcf500596f6094d2eabcd.1498510759.git.tom.zanussi@linux.intel.com> <20170726024019.GA32043@sejong> Content-Type: text/plain; charset="UTF-8" X-Mailer: Evolution 3.10.4 (3.10.4-4.fc20) Mime-Version: 1.0 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi Namhyung, On Wed, 2017-07-26 at 11:40 +0900, Namhyung Kim wrote: > Hi Tom, > > On Mon, Jun 26, 2017 at 05:49:24PM -0500, Tom Zanussi wrote: > > Add an 'onmatch(matching.event).(param list)' > > hist trigger action which is invoked with the set of variables or > > event fields named in the 'param list'. The result is the generation > > of a synthetic event that consists of the values contained in those > > variables and/or fields at the time the invoking event was hit. > > > > As an example the below defines a simple synthetic event using a > > variable defined on the sched_wakeup_new event, and shows the event > > definition with unresolved fields, since the sched_wakeup_new event > > with the testpid variable hasn't been defined yet: > > > > # echo 'wakeup_new_test pid_t pid; int prio' >> \ > > /sys/kernel/debug/tracing/synthetic_events > > > > # cat /sys/kernel/debug/tracing/synthetic_events > > wakeup_new_test pid_t pid; int prio > > > > The following hist trigger both defines a testpid variable and > > specifies an onmatch() trace action that uses that variable along with > > a non-variable field to generate a wakeup_new_test synthetic event > > whenever a sched_wakeup_new event occurs, which because of the 'if > > comm == "cyclictest"' filter only happens when the executable is > > cyclictest: > > > > # echo 'hist:keys=testpid=pid:\ > > onmatch(sched.sched_wakeup_new).wakeup_new_test($testpid, prio) \ > > if comm=="cyclictest"' >> \ > > /sys/kernel/debug/tracing/events/sched/sched_wakeup_new/trigger > > > > Creating and displaying a histogram based on those events is now just > > a matter of using the fields and new synthetic event in the > > tracing/events/synthetic directory, as usual: > > > > # echo 'hist:keys=pid,prio:sort=pid,prio' >> \ > > /sys/kernel/debug/tracing/events/synthetic/wakeup_new_test/trigger > > > > Signed-off-by: Tom Zanussi > > --- > > [SNIP] > > static void hist_trigger_elt_data_free(struct tracing_map_elt *elt) > > { > > + struct hist_trigger_data *hist_data = elt->map->private_data; > > struct hist_elt_data *private_data = elt->private_data; > > + unsigned int i, n_str; > > + > > + n_str = hist_data->n_field_var_str; > > + > > + for (i = 0; i < n_str; i++) > > + kfree(private_data->field_var_str[i]); > > > > kfree(private_data->comm); > > kfree(private_data); > > @@ -1537,7 +1627,7 @@ static int hist_trigger_elt_data_alloc(struct tracing_map_elt *elt) > > unsigned int size = TASK_COMM_LEN + 1; > > struct hist_elt_data *elt_data; > > struct hist_field *key_field; > > - unsigned int i; > > + unsigned int i, n_str; > > > > elt->private_data = elt_data = kzalloc(sizeof(*elt_data), GFP_KERNEL); > > if (!elt_data) > > @@ -1557,6 +1647,16 @@ static int hist_trigger_elt_data_alloc(struct tracing_map_elt *elt) > > } > > } > > > > + n_str = hist_data->n_field_var_str; > > + > > + for (i = 0; i < n_str; i++) { > > + elt_data->field_var_str[i] = kzalloc(size, GFP_KERNEL); > > So the max length of a string variable is TASK_COMM_LEN, right? > Yes, but I think it should be a bit larger - looking at existing events, I also see 32 as a common length, so it would probably be good to up it to that. Unless you have a better idea... > In addition, isn't it necessary for hist_trigger_elt_data_copy() to > copy the field_var_str array? > Yep, missed that, will add. > > > + if (!elt_data->field_var_str[i]) { > > + hist_trigger_elt_data_free(elt); > > + return -ENOMEM; > > + } > > + } > > + > > return 0; > > } > > [SNIP] > > +static bool compatible_keys(struct hist_trigger_data *target_hist_data, > > + struct hist_trigger_data *hist_data, > > + unsigned int n_keys) > > +{ > > + struct hist_field *target_hist_field, *hist_field; > > + unsigned int n, i, j; > > + > > + if (hist_data->n_fields - hist_data->n_vals != n_keys) > > + return false; > > + > > + i = hist_data->n_vals; > > + j = target_hist_data->n_vals; > > + > > + for (n = 0; n < n_keys; n++) { > > + hist_field = hist_data->fields[i + n]; > > + target_hist_field = hist_data->fields[j + n]; > > Shouldn't it be 'target_hist_field = target_hist_data->fields[j + n]'? > ^^^^^^^^^^^^^^^^ > Yeah, thanks for point out the typo. > > + > > + if (strcmp(hist_field->type, target_hist_field->type) != 0) > > + return false; > > + if (hist_field->size != target_hist_field->size) > > + return false; > > + if (hist_field->is_signed != target_hist_field->is_signed) > > + return false; > > + } > > + > > + return true; > > +} > > + > > +static struct hist_trigger_data * > > +find_compatible_hist(struct hist_trigger_data *target_hist_data, > > + struct trace_event_file *file) > > +{ > > + struct hist_trigger_data *hist_data; > > + struct event_trigger_data *test; > > + unsigned int n_keys; > > + > > + n_keys = target_hist_data->n_fields - target_hist_data->n_vals; > > + > > + list_for_each_entry_rcu(test, &file->triggers, list) { > > + if (test->cmd_ops->trigger_type == ETT_EVENT_HIST) { > > + hist_data = test->private_data; > > + > > + if (compatible_keys(target_hist_data, hist_data, n_keys)) > > + return hist_data; > > + } > > + } > > + > > + return NULL; > > +} > > + > > +static struct trace_event_file *event_file(char *system, char *event_name) > > +{ > > + struct trace_event_file *file; > > + struct trace_array *tr; > > + > > + tr = top_trace_array(); > > + if (!tr) > > + return ERR_PTR(-ENODEV); > > + > > + file = find_event_file(tr, system, event_name); > > + if (!file) > > + return ERR_PTR(-EINVAL); > > + > > + return file; > > +} > > + > > +static struct hist_field * > > +create_field_var_hist(struct hist_trigger_data *target_hist_data, > > + char *system, char *event_name, char *field_name) > > IIUC this is needed to create a new hist on a match_event only to > provide a variable for a field, right? I guess it's needed because > adding a new variable is dangerous/unsafe for a running hist. > Exactly. I'll add a comment to make that clear. Thanks, Tom