From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from casper.infradead.org (casper.infradead.org [90.155.50.34]) (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 F08BC35E52C; Mon, 12 Jan 2026 15:31:36 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=90.155.50.34 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1768231905; cv=none; b=XxK3NryZ0e+Nz1H8rt8tkJRwSSs+ac89bm2rc2jwJXcWyi+l9SN/KPx2SBwHkdg+NylM1be/sKeWOhWLdKLc4jesUqEpNbfRU3lV8h6NjTGdSZm6RyLVpGTk3MngNJrCH1intPVHlYVxiGldnNU56VIjwVCQAvE633Ms6Vne4cg= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1768231905; c=relaxed/simple; bh=iNuKlYergc1Qti4EM+/2W5oSqvu/mQWpHDVVV2PTmlA=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=KSlleohkIiJK77RkVgaR5oq8TtAOY/BLmoPb++D3dGdyVUGTCwQR5VjX2Skv8E3MQQSuo5tUq9FFSAHhWy5+4t6P4Yz+7e3syP+QZ01A6lkU0U6EP68TEukz7ednXegPjhuxDvm/i3HHk7qNskES8QaiIMOHzO6Lg4qVzJsr7cw= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=infradead.org; spf=none smtp.mailfrom=infradead.org; dkim=pass (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b=jjNVCcCQ; arc=none smtp.client-ip=90.155.50.34 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=infradead.org Authentication-Results: smtp.subspace.kernel.org; spf=none smtp.mailfrom=infradead.org Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b="jjNVCcCQ" DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=casper.20170209; h=In-Reply-To:Content-Type:MIME-Version: References:Message-ID:Subject:Cc:To:From:Date:Sender:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description; bh=mpvI4NMGhfa99WAkU0UXnKdY/goH2f25zOH4yuWCuBc=; b=jjNVCcCQGFUAfUf/5hIb4rmrOw 9b33Wp8ICmPI8CEfoxZ05ZS4eANhNx1k1OOHjBhAUIGTh9dkm69hGlZqIwN0a2cYdhR+xvJa9RrPl VB9qwwfcFUBbK93wkvDv1p0Zo+dDUM/cXFXckGIODPuU+UQ1RVjfU67sC65Xqme/Sf07I6+YtD+4F tORrrPK9jAe9RRmDcKUPfdkBUerDH86STDdLTX3/xCn3UcGdep0vdZl3PrcR6JFYAzd3FmwP7IfER s9Nb3RMxu105Vx5dyaFmtSJXVMZfGw7kV6tvg9R7O5cGA8gWdVVDz22IJK3x/Ifhykb+l0AmWPhdK Xc3mZ1eQ==; Received: from 2001-1c00-8d85-5700-266e-96ff-fe07-7dcc.cable.dynamic.v6.ziggo.nl ([2001:1c00:8d85:5700:266e:96ff:fe07:7dcc] helo=noisy.programming.kicks-ass.net) by casper.infradead.org with esmtpsa (Exim 4.98.2 #2 (Red Hat Linux)) id 1vfJtB-00000003Pow-1aZN; Mon, 12 Jan 2026 15:31:29 +0000 Received: by noisy.programming.kicks-ass.net (Postfix, from userid 1000) id 4A8C7302D3E; Mon, 12 Jan 2026 16:31:28 +0100 (CET) Date: Mon, 12 Jan 2026 16:31:28 +0100 From: Peter Zijlstra To: Steven Rostedt Cc: Mathieu Desnoyers , Alexei Starovoitov , LKML , Linux trace kernel , bpf , Masami Hiramatsu , "Paul E. McKenney" , Sebastian Andrzej Siewior , Thomas Gleixner , Linus Torvalds Subject: Re: [PATCH v5] tracing: Guard __DECLARE_TRACE() use of __DO_TRACE_CALL() with SRCU-fast Message-ID: <20260112153128.GO830755@noisy.programming.kicks-ass.net> References: <20260108220550.2f6638f3@fedora> <20260109141930.6deb2a0a@gandalf.local.home> <3c0df437-f6e5-47c6-aed5-f4cc26fe627a@efficios.com> <20260109160202.22975aa4@gandalf.local.home> Precedence: bulk X-Mailing-List: linux-trace-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline 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 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.