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=-7.2 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, NICE_REPLY_A,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_SANE_1 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 65260C433E0 for ; Wed, 24 Feb 2021 16:22:57 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 1C29964EDD for ; Wed, 24 Feb 2021 16:22:57 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232806AbhBXQW4 (ORCPT ); Wed, 24 Feb 2021 11:22:56 -0500 Received: from mail.efficios.com ([167.114.26.124]:55156 "EHLO mail.efficios.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S234748AbhBXQWu (ORCPT ); Wed, 24 Feb 2021 11:22:50 -0500 Received: from localhost (localhost [127.0.0.1]) by mail.efficios.com (Postfix) with ESMTP id D16B5314DA7; Wed, 24 Feb 2021 11:22:07 -0500 (EST) Received: from mail.efficios.com ([127.0.0.1]) by localhost (mail03.efficios.com [127.0.0.1]) (amavisd-new, port 10032) with ESMTP id UaOPzPv1u88f; Wed, 24 Feb 2021 11:22:03 -0500 (EST) Received: from localhost (localhost [127.0.0.1]) by mail.efficios.com (Postfix) with ESMTP id 75E44314E2D; Wed, 24 Feb 2021 11:22:03 -0500 (EST) DKIM-Filter: OpenDKIM Filter v2.10.3 mail.efficios.com 75E44314E2D DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=efficios.com; s=default; t=1614183723; bh=RWhpJBj5X6Gn6W/WULJZl80dWN++QmdR7y6Njv4ap7g=; h=To:From:Message-ID:Date:MIME-Version; b=XCVVmaZUekk78Dy+xSiMLSrEzGNvWJwnF0xlJeh8WqxXo/pKOc5AXaTI1YOwx8g5y Zc61OIJriMZQhwpBgCG3rQc0GXTH4Yntj0bS8zFrRAV4w8tQvPlahFHAWjsYZV4Dm9 uj4aAycf/3ScoLIUfos+HzeQQtgp6OcEvf4bbmCr8oaC9SFAy2SEffsp/9VqIO+49y EpJj8Xd0ATykElpgX2qZx28V/ewtnheDkJz80HVUCYrcPnBq+5RbNqKdhIiM5YHX9j SY3d8n9v87+DoKLLpRXkzbvIEvRrHUpXYEgYb8A0FVl3k1Oe1BSPaTT0YZ3pJ10ITY FMBM6AA5agY3Q== X-Virus-Scanned: amavisd-new at efficios.com Received: from mail.efficios.com ([127.0.0.1]) by localhost (mail03.efficios.com [127.0.0.1]) (amavisd-new, port 10026) with ESMTP id i49bEFWWJC29; Wed, 24 Feb 2021 11:22:03 -0500 (EST) Received: from [10.10.0.241] (96-127-212-112.qc.cable.ebox.net [96.127.212.112]) by mail.efficios.com (Postfix) with ESMTPSA id 31B6F314D41; Wed, 24 Feb 2021 11:22:03 -0500 (EST) Subject: Re: [RFC PATCH 0/6] [RFC] Faultable tracepoints (v2) To: Steven Rostedt 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, Mathieu Desnoyers References: <20210218222125.46565-1-mjeanson@efficios.com> <20210223211639.670db85c@gandalf.local.home> From: Michael Jeanson Message-ID: <083bce0f-bd66-ab83-1211-be9838499b45@efficios.com> Date: Wed, 24 Feb 2021 11:22:03 -0500 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.7.1 MIME-Version: 1.0 In-Reply-To: <20210223211639.670db85c@gandalf.local.home> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: bpf@vger.kernel.org [ Adding Mathieu Desnoyers in CC ] On 2021-02-23 21 h 16, Steven Rostedt wrote: > 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 >