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Date: Wed, 22 Jul 2015 15:24:59 -0500
From: Tom Zanussi <tom.zanussi@...ux.intel.com>
To: Masami Hiramatsu <masami.hiramatsu.pt@...achi.com>
Cc: rostedt@...dmis.org, daniel.wagner@...-carit.de,
namhyung@...nel.org, josh@...htriplett.org, andi@...stfloor.org,
linux-kernel@...r.kernel.org
Subject: Re: [PATCH v9 13/22] tracing: Add hist trigger support for clearing
a trace
On Wed, 2015-07-22 at 22:50 +0900, Masami Hiramatsu wrote:
> On 2015/07/17 2:22, Tom Zanussi wrote:
> > Allow users to append 'clear' to an existing trigger in order to have
> > the hash table cleared.
> >
> > This expands the hist trigger syntax from this:
> > # echo hist:keys=xxx:vals=yyy:sort=zzz.descending:pause/cont \
> > [ if filter] > event/trigger
> >
> > to this:
> >
> > # echo hist:keys=xxx:vals=yyy:sort=zzz.descending:pause/cont/clear \
> > [ if filter] > event/trigger
>
> By the way, since pause/cont/clear is not the trigger but the commands
> (which executed immediately), I think it should be a write fops of
> "hist" special file.
>
> e.g. to clear the histogram, write 0 to hist
>
> # echo 0 > event/hist
>
> And pause/cont will be 1 and 2.
>
> # echo 1 > event/hist <- pause
> and
> # echo 2 > event/hist <- continue
>
> What would you think ?
>
I do think it makes sense, and like the idea. But if we allow multiple
histograms per event, does it still work? (I mean in that case, we'd
like to pause/continue/clear them individually, right?)
Tom
> Thanks,
>
>
> >
> > Signed-off-by: Tom Zanussi <tom.zanussi@...ux.intel.com>
> > ---
> > kernel/trace/trace.c | 4 +++-
> > kernel/trace/trace_events_hist.c | 25 ++++++++++++++++++++++++-
> > 2 files changed, 27 insertions(+), 2 deletions(-)
> >
> > diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
> > index 547bbc8..27daa28 100644
> > --- a/kernel/trace/trace.c
> > +++ b/kernel/trace/trace.c
> > @@ -3791,7 +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 [:pause][:continue][:clear]\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"
> > @@ -3826,6 +3826,8 @@ static const char readme_msg[] =
> > "\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"
> > + "\t The 'clear' param will clear the contents of a running hist\n"
> > + "\t trigger and leave its current paused/active state.\n\n"
> > #endif
> > ;
> >
> > diff --git a/kernel/trace/trace_events_hist.c b/kernel/trace/trace_events_hist.c
> > index 3ae58e7..d8259fe 100644
> > --- a/kernel/trace/trace_events_hist.c
> > +++ b/kernel/trace/trace_events_hist.c
> > @@ -80,6 +80,7 @@ struct hist_trigger_attrs {
> > char *sort_key_str;
> > bool pause;
> > bool cont;
> > + bool clear;
> > unsigned int map_bits;
> > };
> >
> > @@ -188,6 +189,8 @@ static struct hist_trigger_attrs *parse_hist_trigger_attrs(char *trigger_str)
> > attrs->sort_key_str = kstrdup(str, GFP_KERNEL);
> > else if (!strncmp(str, "pause", strlen("pause")))
> > attrs->pause = true;
> > + else if (!strncmp(str, "clear", strlen("clear")))
> > + attrs->clear = true;
> > else if (!strncmp(str, "continue", strlen("continue")) ||
> > !strncmp(str, "cont", strlen("cont")))
> > attrs->cont = true;
> > @@ -888,6 +891,24 @@ static struct event_trigger_ops *event_hist_get_trigger_ops(char *cmd,
> > return &event_hist_trigger_ops;
> > }
> >
> > +static void hist_clear(struct event_trigger_data *data)
> > +{
> > + struct hist_trigger_data *hist_data = data->private_data;
> > + bool paused;
> > +
> > + paused = data->paused;
> > + data->paused = true;
> > +
> > + synchronize_sched();
> > +
> > + tracing_map_clear(hist_data->map);
> > +
> > + atomic64_set(&hist_data->total_hits, 0);
> > + atomic64_set(&hist_data->drops, 0);
> > +
> > + data->paused = paused;
> > +}
> > +
> > static int hist_register_trigger(char *glob, struct event_trigger_ops *ops,
> > struct event_trigger_data *data,
> > struct trace_event_file *file)
> > @@ -902,6 +923,8 @@ static int hist_register_trigger(char *glob, struct event_trigger_ops *ops,
> > test->paused = true;
> > else if (hist_data->attrs->cont)
> > test->paused = false;
> > + else if (hist_data->attrs->clear)
> > + hist_clear(test);
> > else
> > ret = -EEXIST;
> > goto out;
> > @@ -1003,7 +1026,7 @@ static int event_hist_trigger_func(struct event_command *cmd_ops,
> > * triggers registered a failure too.
> > */
> > if (!ret) {
> > - if (!(attrs->pause || attrs->cont))
> > + if (!(attrs->pause || attrs->cont || attrs->clear))
> > ret = -ENOENT;
> > goto out_free;
> > } else if (ret < 0)
> >
>
>
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