From: Peter Zijlstra <peterz@infradead.org>
To: Steven Rostedt <rostedt@goodmis.org>
Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>,
Alexei Starovoitov <alexei.starovoitov@gmail.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>,
Linus Torvalds <torvalds@linux-foundation.org>
Subject: Re: [PATCH v5] tracing: Guard __DECLARE_TRACE() use of __DO_TRACE_CALL() with SRCU-fast
Date: Mon, 12 Jan 2026 16:31:28 +0100 [thread overview]
Message-ID: <20260112153128.GO830755@noisy.programming.kicks-ass.net> (raw)
In-Reply-To: <20260109160202.22975aa4@gandalf.local.home>
On Fri, Jan 09, 2026 at 04:02:02PM -0500, Steven Rostedt wrote:
> On Fri, 9 Jan 2026 15:21:19 -0500
> Mathieu Desnoyers <mathieu.desnoyers@efficios.com> wrote:
>
> > * preempt disable/enable pair: 1.1 ns
> > * srcu-fast lock/unlock: 1.5 ns
> >
> > CONFIG_RCU_REF_SCALE_TEST=y
> > * migrate disable/enable pair: 3.0 ns
> > * calls to migrate disable/enable pair within noinline functions: 17.0 ns
> >
> > CONFIG_RCU_REF_SCALE_TEST=m
> > * migrate disable/enable pair: 22.0 ns
>
> OUCH! So migrate disable/enable has a much larger overhead when executed in
> a module than in the kernel? This means all spin_locks() in modules
> converted to mutexes in PREEMPT_RT are taking this hit!
Not so, the migrate_disable() for PREEMPT_RT is still in core code --
kernel/locking/spinlock_rt.c is very much not build as a module.
next prev parent reply other threads:[~2026-01-12 15:31 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 [this message]
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
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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