From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from relay.hostedemail.com (smtprelay0012.hostedemail.com [216.40.44.12]) (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 9410A2FD1C5; Fri, 9 Jan 2026 22:39:20 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=216.40.44.12 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1767998362; cv=none; b=YaDwVy+V3Ne6Y8ozL8nEtWUtu8uGMWabOytLtAPaoz13FR/xGCgO7dbNNkNbAPRZVkdXx2f1BIruwND/WfIKH5kw6fVlVLAkJ7UkbrKVhSHoBnS27yJk1hCv69gduHYPup7TOYZqz9AFWhAGgMNWADTIxede6Xvir2XCSZA8Qj4= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1767998362; c=relaxed/simple; bh=mc1QKo7a3J9z8k1EXgq+/h/3Alt+UI3fXeAa7ve+reI=; h=Date:From:To:Cc:Subject:Message-ID:In-Reply-To:References: MIME-Version:Content-Type; b=KNS2HV+KMW0BjCzmilAIsH1YqdXWAphxqC0hqp8OEghKjRhZXRL2vmm9eCBxB73OhYegzgf1ZHR++uDqIOi+UX5TlvoW3u4zw7kBoYAlshmhZKlSz94CSHH/i0Cy8jpdHOXvHpRiCouMA+VhN/Q9xsIWDcAJNxoAm8jY8Vj5wQ4= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=goodmis.org; spf=pass smtp.mailfrom=goodmis.org; arc=none smtp.client-ip=216.40.44.12 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=goodmis.org Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=goodmis.org Received: from omf14.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay10.hostedemail.com (Postfix) with ESMTP id D1D56C3ECC; Fri, 9 Jan 2026 22:39:18 +0000 (UTC) Received: from [HIDDEN] (Authenticated sender: rostedt@goodmis.org) by omf14.hostedemail.com (Postfix) with ESMTPA id A98A332; Fri, 9 Jan 2026 22:39:16 +0000 (UTC) Date: Fri, 9 Jan 2026 17:39:15 -0500 From: Steven Rostedt To: Alexei Starovoitov Cc: Mathieu Desnoyers , LKML , Linux trace kernel , bpf , Masami Hiramatsu , "Paul E. McKenney" , Sebastian Andrzej Siewior , Thomas Gleixner Subject: Re: [PATCH v5] tracing: Guard __DECLARE_TRACE() use of __DO_TRACE_CALL() with SRCU-fast Message-ID: <20260109173915.1e8a784e@fedora> In-Reply-To: <20260109173326.616e873c@fedora> References: <20260108220550.2f6638f3@fedora> <20260109141930.6deb2a0a@gandalf.local.home> <3c0df437-f6e5-47c6-aed5-f4cc26fe627a@efficios.com> <20260109170028.0068a14d@fedora> <20260109173326.616e873c@fedora> X-Mailer: Claws Mail 4.3.1 (GTK 3.24.51; x86_64-redhat-linux-gnu) Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit X-Rspamd-Queue-Id: A98A332 X-Stat-Signature: aqwm3wgko1hegeu1b8x387j1ngx59fni X-Rspamd-Server: rspamout05 X-Session-Marker: 726F737465647440676F6F646D69732E6F7267 X-Session-ID: U2FsdGVkX1+eunUq5O62J9BP3l8pud2O5GxBVf4ALc0= X-HE-Tag: 1767998356-9069 X-HE-Meta: U2FsdGVkX188sBO5fNYrseaG8Zk5PEAUpvcuW0hLACumdFemnGlyGbV8fPp3oFzztYMy8qg3pnJnnD3U99A1ZCSMpUqjAaMaBmPd2na+fNVBCXmeZY91Ysbw+9UvPYsXWJAANgkaynLPp+KEEm+okZZlhiSjqw6eMo/rSY8qUU/V1FBi6QHVxv8iyLSI5S1RhXZlF8g4/GdJkifisdWFliHxP0SgiN8B4XPJYbrqs/aT0dqF7emTFqCAcU2Tsd+Qe6tndSbwytVmdsDNx6dlhTBo6mrV8oowIikllnDJssNCs3t0zkD0A0KBSr5mRsMmzfVH48TYwk8WTC70IGkF/R7OS3pVQrgClnD/s4IaPpaRdipVoR+iUCWR3jZTVPDI On Fri, 9 Jan 2026 17:33:26 -0500 Steven Rostedt 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