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Date: Wed, 22 Jul 2015 17:20:12 +0900
From: Masami Hiramatsu <masami.hiramatsu.pt@...achi.com>
To: Tom Zanussi <tom.zanussi@...ux.intel.com>, rostedt@...dmis.org
CC: daniel.wagner@...-carit.de, namhyung@...nel.org,
josh@...htriplett.org, andi@...stfloor.org,
linux-kernel@...r.kernel.org
Subject: Re: [PATCH v9 12/22] tracing: Add hist trigger support for pausing
and continuing a trace
Hi Tom,
On 2015/07/17 2:22, Tom Zanussi wrote:
> Allow users to append 'pause' or 'continue' to an existing trigger in
> order to have it paused or to have a paused trace continue.
>
> This expands the hist trigger syntax from this:
> # echo hist:keys=xxx:vals=yyy:sort=zzz.descending \
> [ if filter] > event/trigger
>
> to this:
>
> # echo hist:keys=xxx:vals=yyy:sort=zzz.descending:pause or cont \
> [ if filter] > event/trigger
Since the only one hist trigger can be set on one event, it seems
that we don't need keys for pause/cont/clear (e.g. hist:pause is enough).
Anyway, I've found an odd behavior.
[root@...alhost tracing]# echo 'hist:keys=parent_pid' > events/sched/sched_process_fork/trigger
[root@...alhost tracing]# echo 'hist:keys=common_pid:pause' > events/sched/sched_process_fork/trigger
[root@...alhost tracing]# cat events/sched/sched_process_fork/trigger
hist:keys=parent_pid:vals=hitcount:sort=hitcount:size=2048 [paused]
So, the second "pause" command can work with different keys.
Moreover, I can remove it with different keys.
[root@...alhost tracing]# echo '!hist:keys=child_pid' > events/sched/sched_process_fork/trigger
[root@...alhost tracing]# cat events/sched/sched_process_fork/trigger
# Available triggers:
# traceon traceoff snapshot stacktrace enable_event disable_event enable_hist disable_hist hist
Thank you,
>
> Signed-off-by: Tom Zanussi <tom.zanussi@...ux.intel.com>
> ---
> kernel/trace/trace.c | 5 +++++
> kernel/trace/trace_events_hist.c | 26 +++++++++++++++++++++++---
> 2 files changed, 28 insertions(+), 3 deletions(-)
>
> diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
> index 5dd1fc4..547bbc8 100644
> --- a/kernel/trace/trace.c
> +++ b/kernel/trace/trace.c
> @@ -3791,6 +3791,7 @@ static const char readme_msg[] =
> "\t [:values=<field1[,field2,...]]\n"
> "\t [:sort=field1,field2,...]\n"
> "\t [:size=#entries]\n"
> + "\t [:pause][:continue]\n"
> "\t [if <filter>]\n\n"
> "\t When a matching event is hit, an entry is added to a hash\n"
> "\t table using the key(s) and value(s) named. Keys and values\n"
> @@ -3821,6 +3822,10 @@ static const char readme_msg[] =
> "\t on. The default if unspecified is 'hitcount' and the.\n"
> "\t default sort order is 'ascending'. To sort in the opposite\n"
> "\t direction, append .descending' to the sort key.\n\n"
> + "\t The 'pause' param can be used to pause an existing hist\n"
> + "\t trigger or to start a hist trigger but not log any events\n"
> + "\t until told to do so. 'continue' can be used to start or\n"
> + "\t restart a paused hist trigger.\n\n"
> #endif
> ;
>
> diff --git a/kernel/trace/trace_events_hist.c b/kernel/trace/trace_events_hist.c
> index 6bf224f..3ae58e7 100644
> --- a/kernel/trace/trace_events_hist.c
> +++ b/kernel/trace/trace_events_hist.c
> @@ -78,6 +78,8 @@ struct hist_trigger_attrs {
> char *keys_str;
> char *vals_str;
> char *sort_key_str;
> + bool pause;
> + bool cont;
> unsigned int map_bits;
> };
>
> @@ -184,6 +186,11 @@ static struct hist_trigger_attrs *parse_hist_trigger_attrs(char *trigger_str)
> attrs->vals_str = kstrdup(str, GFP_KERNEL);
> else if (!strncmp(str, "sort", strlen("sort")))
> attrs->sort_key_str = kstrdup(str, GFP_KERNEL);
> + else if (!strncmp(str, "pause", strlen("pause")))
> + attrs->pause = true;
> + else if (!strncmp(str, "continue", strlen("continue")) ||
> + !strncmp(str, "cont", strlen("cont")))
> + attrs->cont = true;
> else if (!strncmp(str, "size", strlen("size"))) {
> int map_bits = parse_map_size(str);
>
> @@ -843,7 +850,10 @@ static int event_hist_trigger_print(struct seq_file *m,
> if (data->filter_str)
> seq_printf(m, " if %s", data->filter_str);
>
> - seq_puts(m, " [active]");
> + if (data->paused)
> + seq_puts(m, " [paused]");
> + else
> + seq_puts(m, " [active]");
>
> seq_putc(m, '\n');
>
> @@ -882,16 +892,25 @@ static int hist_register_trigger(char *glob, struct event_trigger_ops *ops,
> struct event_trigger_data *data,
> struct trace_event_file *file)
> {
> + struct hist_trigger_data *hist_data = data->private_data;
> struct event_trigger_data *test;
> int ret = 0;
>
> list_for_each_entry_rcu(test, &file->triggers, list) {
> if (test->cmd_ops->trigger_type == ETT_EVENT_HIST) {
> - ret = -EEXIST;
> + if (hist_data->attrs->pause)
> + test->paused = true;
> + else if (hist_data->attrs->cont)
> + test->paused = false;
> + else
> + ret = -EEXIST;
> goto out;
> }
> }
>
> + if (hist_data->attrs->pause)
> + data->paused = true;
> +
> if (data->ops->init) {
> ret = data->ops->init(data->ops, data);
> if (ret < 0)
> @@ -984,7 +1003,8 @@ static int event_hist_trigger_func(struct event_command *cmd_ops,
> * triggers registered a failure too.
> */
> if (!ret) {
> - ret = -ENOENT;
> + if (!(attrs->pause || attrs->cont))
> + ret = -ENOENT;
> goto out_free;
> } else if (ret < 0)
> goto out_free;
>
--
Masami HIRAMATSU
Linux Technology Research Center, System Productivity Research Dept.
Center for Technology Innovation - Systems Engineering
Hitachi, Ltd., Research & Development Group
E-mail: masami.hiramatsu.pt@...achi.com
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