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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id AEFAFC433F5 for ; Mon, 25 Apr 2022 16:02:58 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S243121AbiDYQGB (ORCPT ); Mon, 25 Apr 2022 12:06:01 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:39288 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S243195AbiDYQF7 (ORCPT ); Mon, 25 Apr 2022 12:05:59 -0400 Received: from mail.efficios.com (mail.efficios.com [167.114.26.124]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 23BC112611 for ; Mon, 25 Apr 2022 09:02:54 -0700 (PDT) Received: from localhost (localhost [127.0.0.1]) by mail.efficios.com (Postfix) with ESMTP id 1E67B3CF1E2; Mon, 25 Apr 2022 12:02:53 -0400 (EDT) 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 nUJgFl7voe_k; Mon, 25 Apr 2022 12:02:52 -0400 (EDT) Received: from localhost (localhost [127.0.0.1]) by mail.efficios.com (Postfix) with ESMTP id 767C43CF469; Mon, 25 Apr 2022 12:02:52 -0400 (EDT) DKIM-Filter: OpenDKIM Filter v2.10.3 mail.efficios.com 767C43CF469 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=efficios.com; s=default; t=1650902572; bh=j6y8wcrhdZ6ADgcS4e0rv9G8+EgKKSu6ZlEe9Iow5gw=; h=Date:From:To:Message-ID:MIME-Version; b=QXNthuqaM9+A0nKFeD/CY0reoTyY2U2YUJ+N1dH+Hfk3yf5Xe6nVQG5ma3PxVIfUe 4klXa2OqfaXZwHq0/y6oITHNrvsIiJgCWBpznrSWav5y4E5y0EsKYnQLE4uRSa3nOS EXGfl4IVKfEKs5+TcJSN6ssoS4Ce2qMbLe/p+h/eLZsg2tBsgHwdZEg11sHOmmLjgQ nwXe+K6WeZzjV3jE+DpBP+hLSVa3HAZGyr4CukPLm4r2pBWFe5+oujto1dKkmlJu1w pOuOr/aqvfdpHsJStkLWmJFy1DTIkRwqMfMzwFKwSTiMEYGTuUajRXGDTP3wXCMp+/ dI/Bj8sr+odBg== 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 GlP_LFzoRsYa; Mon, 25 Apr 2022 12:02:52 -0400 (EDT) Received: from mail03.efficios.com (mail03.efficios.com [167.114.26.124]) by mail.efficios.com (Postfix) with ESMTP id 684F43CF1DF; Mon, 25 Apr 2022 12:02:52 -0400 (EDT) Date: Mon, 25 Apr 2022 12:02:52 -0400 (EDT) From: Mathieu Desnoyers To: Steven Rostedt Cc: Paolo Bonzini , Sean Christopherson , KVM list , lttng-dev , Michael Jeanson Message-ID: <892959086.34940.1650902572304.JavaMail.zimbra@efficios.com> In-Reply-To: <20220425100434.2f5d18bb@gandalf.local.home> References: <1218866473.10909.1649432186473.JavaMail.zimbra@efficios.com> <3c11308e-006a-a7e9-8482-c6b341690530@redhat.com> <1622857974.11247.1649441213797.JavaMail.zimbra@efficios.com> <20220425100434.2f5d18bb@gandalf.local.home> Subject: Re: Unexport of kvm_x86_ops vs tracer modules MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit X-Originating-IP: [167.114.26.124] X-Mailer: Zimbra 8.8.15_GA_4257 (ZimbraWebClient - FF99 (Linux)/8.8.15_GA_4257) Thread-Topic: Unexport of kvm_x86_ops vs tracer modules Thread-Index: gjp2UP+GQzqompjQk+kWzrxYc4diFA== Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.org ----- On Apr 25, 2022, at 10:04 AM, Steven Rostedt rostedt@goodmis.org wrote: > On Fri, 8 Apr 2022 14:06:53 -0400 (EDT) > Mathieu Desnoyers wrote: >> >> Indeed, the fact that the TP_fast_assign snippets are embedded in the >> trace_event_raw_event_* symbols is an issue for LTTng. This ties those >> to ftrace. > > Not just ftrace, perf does it too. > > Now another solution is to make the fast assigns available to anyone, and > to allow you to simply pass in a pointer and size to have the data written > into it. That is, you get the results of the TRACE_EVENT and not have to > depend on internal data from the tracepoint. If the fast assign can then be used on a field-per-field basis, maybe this could work, but AFAIK the fast-assign macro is open-coded C, which makes this not straightforward. If it's a all-or-nothing approach where the fast-assign needs to serialize all fields, this would require that lttng copies the data into a temporary area, which is something I want to avoid for filtering and event notification per-field payload capture purposes. Thanks, Mathieu -- Mathieu Desnoyers EfficiOS Inc. http://www.efficios.com