From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 4FB1422D7B5; Wed, 3 Dec 2025 22:39:03 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1764801547; cv=none; b=MkYzGiTeGaSc/KeD+N3ZG6QhJEWml0C87KEJz0ROvt8oLhxBsBw1TGzdmE9q5tRrdrvOKKRQDWeMvVsJRT4B73F3GMJCOTpgizcM2jpqQhX4vJNjb61i5wa3hlrgCDhvoCZWKhbKVMFe9UDPd96hy6Ib/5W+6ZZsuTjk1J3tHjg= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1764801547; c=relaxed/simple; bh=jCQ1gASlQztHfXgp6fI53DhEfp9d/b6de4+33+Ar5Ds=; h=Message-ID:Subject:From:To:Cc:Date:In-Reply-To:References: Content-Type:MIME-Version; b=K/YcCjEkjDxrHoTZXtIUFvX09rvJwfCBUCcjV3amGWf6s7VYxZ1r0YX1CAXYzaTlz2o9+006DUI5WP1weB+Lb5YfoWRApEleTPeu2go9P7VT8J+P4+UYhNpgYqCqTGsBBIizPtShHabNYZB1FehTmtTcklkukVHBdKrRpOl3M1o= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=c3wUQeww; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="c3wUQeww" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 4685EC4CEF5; Wed, 3 Dec 2025 22:39:03 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1764801543; bh=jCQ1gASlQztHfXgp6fI53DhEfp9d/b6de4+33+Ar5Ds=; h=Subject:From:To:Cc:Date:In-Reply-To:References:From; b=c3wUQewwpSUWHN7K0NqeEk5gj/Wm2Opsq4wISWOuhSb4WZNJBIK9X58Z2DpBlh9dZ 97o/EVZfuFkQ7lssmXJIeSFHDK5xavYLziT0OCFBV5M8/MjmKujd1w49JRWu0/spml Tpz9hVYd/2TcjUvij82JqbDnKf19wrV+ucMJoMB5dHabLcihB4QVhHvnL0BUjj2YWC Yik5RIHo9tVIHwy/eEHeAs4VAlMZ2RLP/FzuWT91Yg0Suqmca9IdHZMzrKBIFkL8jx 5CwW/9bG+O/KFCo4Pi7/1AV5QCxSy9aC680rTh++wdgVHW1xK7mvXvps2Pz08J8SIo 4W75Le2qoTc8A== Message-ID: <383568a33fdca98e08b38dc16079e57ad88c0d44.camel@kernel.org> Subject: Re: [PATCH v2 2/3] tracing: Add bulk garbage collection of freeing event_trigger_data From: Tom Zanussi To: Steven Rostedt , linux-kernel@vger.kernel.org, linux-trace-kernel@vger.kernel.org Cc: Masami Hiramatsu , Mark Rutland , Mathieu Desnoyers , Andrew Morton Date: Wed, 03 Dec 2025 16:39:02 -0600 In-Reply-To: <20251125214032.151674992@kernel.org> References: <20251125214004.396482401@kernel.org> <20251125214032.151674992@kernel.org> Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable User-Agent: Evolution 3.52.3-0ubuntu1 Precedence: bulk X-Mailing-List: linux-trace-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 On Tue, 2025-11-25 at 16:40 -0500, Steven Rostedt wrote: > From: Steven Rostedt >=20 > The event trigger data requires a full tracepoint_synchronize_unregister(= ) > call before freeing. That call can take 100s of milliseconds to complete. > In order to allow for bulk freeing of the trigger data, it can not call > the tracepoint_synchronize_unregister() for every individual trigger data > being free. >=20 > Create a kthread that gets created the first time a trigger data is freed= , > and have it use the lockless llist to get the list of data to free, run > the tracepoint_synchronize_unregister() then free everything in the list. >=20 > By freeing hundreds of event_trigger_data elements together, it only > requires two runs of the synchronization function, and not hundreds of > runs. This speeds up the operation by orders of magnitude (milliseconds > instead of several seconds). >=20 > Acked-by: Masami Hiramatsu (Google) > Signed-off-by: Steven Rostedt (Google) Very nice! Reviewed-by: Tom Zanussi > --- > Changes since v1: https://patch.msgid.link/20251120205710.151041470@kerne= l.org >=20 > - Moved include of llist.h to trace.h as it is used there (Masami Hiramat= su) >=20 > =C2=A0kernel/trace/trace.h=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2= =A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 |=C2=A0 2 ++ > =C2=A0kernel/trace/trace_events_trigger.c | 55 ++++++++++++++++++++++++++= +-- > =C2=A02 files changed, 54 insertions(+), 3 deletions(-) >=20 > diff --git a/kernel/trace/trace.h b/kernel/trace/trace.h > index 5863800b1ab3..911fc75dc6c4 100644 > --- a/kernel/trace/trace.h > +++ b/kernel/trace/trace.h > @@ -22,6 +22,7 @@ > =C2=A0#include > =C2=A0#include > =C2=A0#include > +#include > =C2=A0 > =C2=A0#include "pid_list.h" > =C2=A0 > @@ -1808,6 +1809,7 @@ struct event_trigger_data { > =C2=A0 char *name; > =C2=A0 struct list_head named_list; > =C2=A0 struct event_trigger_data *named_data; > + struct llist_node llist; > =C2=A0}; > =C2=A0 > =C2=A0/* Avoid typos */ > diff --git a/kernel/trace/trace_events_trigger.c b/kernel/trace/trace_eve= nts_trigger.c > index e5dcfcbb2cd5..3b97c242b795 100644 > --- a/kernel/trace/trace_events_trigger.c > +++ b/kernel/trace/trace_events_trigger.c > @@ -6,6 +6,7 @@ > =C2=A0 */ > =C2=A0 > =C2=A0#include > +#include > =C2=A0#include > =C2=A0#include > =C2=A0#include > @@ -17,15 +18,63 @@ > =C2=A0static LIST_HEAD(trigger_commands); > =C2=A0static DEFINE_MUTEX(trigger_cmd_mutex); > =C2=A0 > +static struct task_struct *trigger_kthread; > +static struct llist_head trigger_data_free_list; > +static DEFINE_MUTEX(trigger_data_kthread_mutex); > + > +/* Bulk garbage collection of event_trigger_data elements */ > +static int trigger_kthread_fn(void *ignore) > +{ > + struct event_trigger_data *data, *tmp; > + struct llist_node *llnodes; > + > + /* Once this task starts, it lives forever */ > + for (;;) { > + set_current_state(TASK_INTERRUPTIBLE); > + if (llist_empty(&trigger_data_free_list)) > + schedule(); > + > + __set_current_state(TASK_RUNNING); > + > + llnodes =3D llist_del_all(&trigger_data_free_list); > + > + /* make sure current triggers exit before free */ > + tracepoint_synchronize_unregister(); > + > + llist_for_each_entry_safe(data, tmp, llnodes, llist) > + kfree(data); > + } > + > + return 0; > +} > + > =C2=A0void trigger_data_free(struct event_trigger_data *data) > =C2=A0{ > =C2=A0 if (data->cmd_ops->set_filter) > =C2=A0 data->cmd_ops->set_filter(NULL, data, NULL); > =C2=A0 > - /* make sure current triggers exit before free */ > - tracepoint_synchronize_unregister(); > + if (unlikely(!trigger_kthread)) { > + guard(mutex)(&trigger_data_kthread_mutex); > + /* Check again after taking mutex */ > + if (!trigger_kthread) { > + struct task_struct *kthread; > + > + kthread =3D kthread_create(trigger_kthread_fn, NULL, > + "trigger_data_free"); > + if (!IS_ERR(kthread)) > + WRITE_ONCE(trigger_kthread, kthread); > + } > + } > + > + if (!trigger_kthread) { > + /* Do it the slow way */ > + tracepoint_synchronize_unregister(); > + kfree(data); > + return; > + } > =C2=A0 > - kfree(data); > + llist_add(&data->llist, &trigger_data_free_list); > + wake_up_process(trigger_kthread); > =C2=A0} > =C2=A0 > =C2=A0static inline void data_ops_trigger(struct event_trigger_data *data= ,