From: Steven Rostedt <rostedt@goodmis.org>
To: Alexei Starovoitov <alexei.starovoitov@gmail.com>
Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>,
LKML <linux-kernel@vger.kernel.org>,
Linux trace kernel <linux-trace-kernel@vger.kernel.org>,
bpf <bpf@vger.kernel.org>, Masami Hiramatsu <mhiramat@kernel.org>,
"Paul E. McKenney" <paulmck@kernel.org>,
Sebastian Andrzej Siewior <bigeasy@linutronix.de>,
Thomas Gleixner <tglx@linutronix.de>
Subject: Re: [PATCH v5] tracing: Guard __DECLARE_TRACE() use of __DO_TRACE_CALL() with SRCU-fast
Date: Fri, 9 Jan 2026 17:39:15 -0500 [thread overview]
Message-ID: <20260109173915.1e8a784e@fedora> (raw)
In-Reply-To: <20260109173326.616e873c@fedora>
On Fri, 9 Jan 2026 17:33:26 -0500
Steven Rostedt <rostedt@goodmis.org> wrote:
> How is this about lttng? Sure he cares about that, but even tracepoints
> that lttng uses doesn't get affected any more than ftrace or bpf.
> Because lttng is one of the callbacks. The migrate disable happens in
> the in-tree portion of the code.
>
> So you are saying that all the tracepoints for xfs are not in a fastpath?
Regardless of tracing. I now have my RT hat on. The spin_locks that are
converted to mutex use migrate disable. The fact that migrate_disable
in modules are close to 10x slower than the same code in-kernel is
troubling to say the least. It means that modules in RT take a hit
every time they take a spin_lock().
The migrate disable being slow for modules is no longer just a tracing
issue. It's a PREEMPT_RT issue.
-- Steve
next prev parent reply other threads:[~2026-01-09 22:39 UTC|newest]
Thread overview: 29+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-01-09 3:05 [PATCH v5] tracing: Guard __DECLARE_TRACE() use of __DO_TRACE_CALL() with SRCU-fast Steven Rostedt
2026-01-09 14:40 ` Mathieu Desnoyers
2026-01-09 17:21 ` Steven Rostedt
2026-01-09 18:58 ` Mathieu Desnoyers
2026-01-13 13:56 ` Sebastian Andrzej Siewior
2026-01-09 19:10 ` Alexei Starovoitov
2026-01-09 19:19 ` Steven Rostedt
2026-01-09 20:21 ` Mathieu Desnoyers
2026-01-09 21:02 ` Steven Rostedt
2026-01-12 7:23 ` Menglong Dong
2026-01-12 15:31 ` Peter Zijlstra
2026-01-12 15:36 ` Steven Rostedt
2026-01-12 15:44 ` Peter Zijlstra
2026-01-09 21:54 ` Alexei Starovoitov
2026-01-09 22:00 ` Steven Rostedt
2026-01-09 22:18 ` Alexei Starovoitov
2026-01-09 22:31 ` Mathieu Desnoyers
2026-01-09 22:33 ` Steven Rostedt
2026-01-09 22:39 ` Steven Rostedt [this message]
2026-01-10 0:35 ` Alexei Starovoitov
2026-01-10 16:14 ` Steven Rostedt
2026-01-11 20:04 ` Alexei Starovoitov
2026-01-11 22:09 ` Steven Rostedt
2026-01-11 23:38 ` Alexei Starovoitov
2026-01-12 13:53 ` Steven Rostedt
2026-01-12 17:19 ` Alexei Starovoitov
2026-01-13 14:23 ` Sebastian Andrzej Siewior
2026-01-13 23:44 ` Alexei Starovoitov
2026-01-09 19:19 ` Yonghong Song
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