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Message-ID: <20240301153001.0d544f9c@gandalf.local.home>
Date: Fri, 1 Mar 2024 15:30:01 -0500
From: Steven Rostedt <rostedt@...dmis.org>
To: "Paul E. McKenney" <paulmck@...nel.org>
Cc: linux-trace-kernel@...r.kernel.org, linux-kernel@...r.kernel.org, Masami
Hiramatsu <mhiramat@...nel.org>, Mark Rutland <mark.rutland@....com>,
Mathieu Desnoyers <mathieu.desnoyers@...icios.com>, Ankur Arora
<ankur.a.arora@...cle.com>, Thomas Gleixner <tglx@...utronix.de>,
kernel-team@...a.com
Subject: Re: [PATCH RFC ftrace] Chose RCU Tasks based on TASKS_RCU rather
than PREEMPTION
On Fri, 1 Mar 2024 12:25:10 -0800
"Paul E. McKenney" <paulmck@...nel.org> wrote:
> > That would work for me. If there are no objections, I will make this
> > change.
>
> But I did check the latency of synchronize_rcu_tasks_rude() (about 100ms)
> and synchronize_rcu() (about 20ms). This is on a 80-hardware-thread
> x86 system that is being flooded with calls to one or the other of
> these two functions, but is otherwise idle. So adding that unnecessary
> synchronize_rcu() adds about 20% to that synchronization delay.
>
> Which might still be OK, but... In the immortal words of MS-DOS,
> "Are you sure?". ;-)
It's just safe to keep it. It's definitely not a fast path.
-- Steve
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