From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-5.2 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED,USER_AGENT_SANE_2 autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 527CDC433DB for ; Wed, 24 Feb 2021 02:17:42 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id EB69D64E85 for ; Wed, 24 Feb 2021 02:17:41 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232148AbhBXCRZ (ORCPT ); Tue, 23 Feb 2021 21:17:25 -0500 Received: from mail.kernel.org ([198.145.29.99]:55888 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229961AbhBXCRX (ORCPT ); Tue, 23 Feb 2021 21:17:23 -0500 Received: from gandalf.local.home (cpe-66-24-58-225.stny.res.rr.com [66.24.58.225]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 465A564E7A; Wed, 24 Feb 2021 02:16:41 +0000 (UTC) Date: Tue, 23 Feb 2021 21:16:39 -0500 From: Steven Rostedt To: Michael Jeanson Cc: linux-kernel@vger.kernel.org, Peter Zijlstra , Alexei Starovoitov , Yonghong Song , "Paul E . McKenney" , Ingo Molnar , Arnaldo Carvalho de Melo , Mark Rutland , Alexander Shishkin , Jiri Olsa , Namhyung Kim , Joel Fernandes , bpf@vger.kernel.org Subject: Re: [RFC PATCH 0/6] [RFC] Faultable tracepoints (v2) Message-ID: <20210223211639.670db85c@gandalf.local.home> In-Reply-To: <20210218222125.46565-1-mjeanson@efficios.com> References: <20210218222125.46565-1-mjeanson@efficios.com> X-Mailer: Claws Mail 3.17.8 (GTK+ 2.24.33; x86_64-pc-linux-gnu) MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, 18 Feb 2021 17:21:19 -0500 Michael Jeanson wrote: > This series only implements the tracepoint infrastructure required to > allow tracers to handle page faults. Modifying each tracer to handle > those page faults would be a next step after we all agree on this piece > of instrumentation infrastructure. I started taking a quick look at this, and came up with the question: how do you allow preemption when dealing with per-cpu buffers or storage to record the data? That is, perf, bpf and ftrace are all using some kind of per-cpu data, and this is the reason for the need to disable preemption. What's the solution that LTTng is using for this? I know it has a per cpu buffers too, but does it have some kind of "per task" buffer that is being used to extract the data that can fault? -- Steve