From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.129.124]) (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 491253B634F for ; Fri, 13 Mar 2026 15:36:25 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=170.10.129.124 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1773416188; cv=none; b=QqiFRQOcB7djxlEXBJpTBETHBQ51t/QIEp+pb2jC9WB1SgUdj8jw2IJL/4AhttYm+CKskcsWR72ipPIu49fEiOZlDhxMpFOCawbPNcLb5xJtRQhr6wuXkBegnf9VugKQHlZdlOJyffho79dgnNoJH4wc58pxwbsF/0BMv42GMPM= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1773416188; c=relaxed/simple; bh=CyCGUMD3VoVbcPs264yI0PvIDuyg8kPmxW1bTL+plGg=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: In-Reply-To:Content-Type:Content-Disposition; b=Ccj70w6j31aQtfJS6aCkjc6Br+STJUQQaFSWEQdh8tD6on4VECc2SpDvVqQzPd/CZsbiMdst6ibdjJdXTbc5CKLfDWlBd7wCukIB+Xmkkx0c4ohmHxvzD936GNiSBFVr1l8a/vqhkIDK8JkZZffIwWXEpCA7QnujZpJvOuL2Yhk= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=redhat.com; spf=pass smtp.mailfrom=redhat.com; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b=fNZaqAej; arc=none smtp.client-ip=170.10.129.124 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=redhat.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=redhat.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="fNZaqAej" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1773416184; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=8YOawQNVQkIo70h92e1d8c2a75rIGeMZJhaqZP76hJU=; b=fNZaqAejtdyhlX0lj4oX+VZOQHEGLGGVbg1wjLz3q2FJSSH1Fzg7wyY/tQZTXZt362mx62 0kKmNGYS0Iu3kyKH9XnrNRY1Qe6fZZaXMFNEH3FoiMGfb/MC3K2fd9Lo19yrbfvOa1ctRs qxqWTPujIk+3hPMQoZzyieLtEetkhEQ= Received: from mx-prod-mc-05.mail-002.prod.us-west-2.aws.redhat.com (ec2-54-186-198-63.us-west-2.compute.amazonaws.com [54.186.198.63]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-691-r3Sdx55OOqOtQwgAUmxByQ-1; Fri, 13 Mar 2026 11:36:20 -0400 X-MC-Unique: r3Sdx55OOqOtQwgAUmxByQ-1 X-Mimecast-MFC-AGG-ID: r3Sdx55OOqOtQwgAUmxByQ_1773416179 Received: from mx-prod-int-05.mail-002.prod.us-west-2.aws.redhat.com (mx-prod-int-05.mail-002.prod.us-west-2.aws.redhat.com [10.30.177.17]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits) server-digest SHA256) (No client certificate requested) by mx-prod-mc-05.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id 67509195609D; Fri, 13 Mar 2026 15:36:18 +0000 (UTC) Received: from fedora (unknown [10.22.81.255]) by mx-prod-int-05.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTP id 10B6E19540C2; Fri, 13 Mar 2026 15:36:11 +0000 (UTC) Date: Fri, 13 Mar 2026 12:36:10 -0300 From: Wander Lairson Costa To: Peter Zijlstra Cc: Ingo Molnar , Juri Lelli , Vincent Guittot , Dietmar Eggemann , Steven Rostedt , Ben Segall , Mel Gorman , Valentin Schneider , Masami Hiramatsu , Mathieu Desnoyers , Andrew Morton , "open list:SCHEDULER" , "open list:TRACING" , acme@kernel.org, williams@redhat.com, gmonaco@redhat.com Subject: Re: [PATCH v3 1/4] tracing/preemptirq: Optimize preempt_disable/enable() tracepoint overhead Message-ID: References: <20260311125021.197638-1-wander@redhat.com> <20260311125021.197638-2-wander@redhat.com> <20260311193503.GS606826@noisy.programming.kicks-ass.net> <20260313090404.GK606826@noisy.programming.kicks-ass.net> Precedence: bulk X-Mailing-List: linux-trace-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 In-Reply-To: <20260313090404.GK606826@noisy.programming.kicks-ass.net> X-Scanned-By: MIMEDefang 3.0 on 10.30.177.17 X-Mimecast-MFC-PROC-ID: uQJ7m3B_z_5UIhUaBNEwqhp2h8nqxKN4eif711RZpaA_1773416179 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit On Fri, Mar 13, 2026 at 10:04:04AM +0100, Peter Zijlstra wrote: > On Thu, Mar 12, 2026 at 02:19:15PM -0300, Wander Lairson Costa wrote: > > > > That's significant bloat, for really very little gain. Realistically > > > nobody is going to need these. > > > > > > > Of course, I can't speak for others, but more than once I debugged issues > > that those tracepoints had made my life far easier. Those cases convinced > > me that such a feature would be worth it. But if you don't see > > value and will reject the patches no matter what, nothing can be done, > > and I will have to accept defeat. > > If distros are going to enable this, I suppose I'm not going to stop > this. But I do very much worry about the general bloat of things, there > are a *LOT* of preempt_{dis,en}able() sites. > We plan to enable these tracepoints in the RHEL kernel-rt to track extended non-preemptible states that cause high latencies. These issues occasionally surface in customer OpenShift deployments, where deploying a custom debug kernel is highly impractical. Having these tracepoints available in the distribution kernel would be handful for debugging these production systems. That said, I expect enabling this feature to be the exception rather than the rule — most distribution kernels would leave it disabled.