Messages in this thread Patch in this message | | | Date | Sat, 30 Sep 2023 04:03:57 -0400 | From | Steven Rostedt <> | Subject | Re: [PATCH] trace: tracing_event_filter: fast path when no subsystem filters |
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On Tue, 26 Sep 2023 10:20:58 -0400 Nicholas Lowell <nicholas.lowell@gmail.com> wrote:
> From: Nicholas Lowell <nlowell@lexmark.com> > > If there are no filters in the event subsystem, then there's no > reason to continue and hit the potentially time consuming > tracepoint_synchronize_unregister function. This should give > a speed up for initial disabling/configuring > > Signed-off-by: Nicholas Lowell <nlowell@lexmark.com> > --- > kernel/trace/trace_events_filter.c | 19 ++++++++++++++----- > 1 file changed, 14 insertions(+), 5 deletions(-) > > diff --git a/kernel/trace/trace_events_filter.c b/kernel/trace/trace_events_filter.c > index 33264e510d16..93653d37a132 100644 > --- a/kernel/trace/trace_events_filter.c > +++ b/kernel/trace/trace_events_filter.c > @@ -1317,22 +1317,29 @@ void free_event_filter(struct event_filter *filter) > __free_filter(filter); > } > > -static inline void __remove_filter(struct trace_event_file *file) > +static inline int __remove_filter(struct trace_event_file *file) > { > filter_disable(file); > - remove_filter_string(file->filter); > + if (file->filter) > + remove_filter_string(file->filter); > + else > + return 0; > + > + return 1;
The above looks awkward. What about:
if (!file->filter) return 0;
remove_filter_string(file->filter); return 1;
?
Or better yet:
if (!file->filter) return false;
remove_filter_string(file->filter); return true;
and ...
> } > > -static void filter_free_subsystem_preds(struct trace_subsystem_dir *dir, > +static int filter_free_subsystem_preds(struct trace_subsystem_dir *dir, > struct trace_array *tr) > { > struct trace_event_file *file; > + int i = 0;
We don't really need a counter. It's either do the synchronization or we don't.
bool do_sync = false;
> > list_for_each_entry(file, &tr->events, list) { > if (file->system != dir) > continue; > - __remove_filter(file); > + i += __remove_filter(file);
if (remove_filter(file)) do_sync = true;
> }
return do_sync;
> + return i; > } > > static inline void __free_subsystem_filter(struct trace_event_file *file) > @@ -2411,7 +2418,9 @@ int apply_subsystem_event_filter(struct trace_subsystem_dir *dir, > } > > if (!strcmp(strstrip(filter_string), "0")) { > - filter_free_subsystem_preds(dir, tr); > + if (filter_free_subsystem_preds(dir, tr) == 0) > + goto out_unlock; > +
/* If nothing was freed, we do not need to sync */ if (!filter_free_subsystem_preds(dir, tr)) goto out_unlock;
And yes, add the comment.
And actually, in that block with the goto out_unlock, we should have:
if (!filter_free_subsystem_preds(dir, tr)) { if (!(WARN_ON_ONCE(system->filter)) goto out_unlock; }
If there were no preds, ideally there would be no subsystem filter. But if that's not the case, we need to warn about that and then continue.
-- Steve > remove_filter_string(system->filter); > filter = system->filter; > system->filter = NULL;
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