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=-1.0 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_PASS autolearn=ham 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 538F7C43441 for ; Fri, 9 Nov 2018 18:42:47 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 1B65920827 for ; Fri, 9 Nov 2018 18:42:47 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 1B65920827 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=goodmis.org Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728685AbeKJEYe (ORCPT ); Fri, 9 Nov 2018 23:24:34 -0500 Received: from mail.kernel.org ([198.145.29.99]:54592 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727995AbeKJEYd (ORCPT ); Fri, 9 Nov 2018 23:24:33 -0500 Received: from gandalf.local.home (cpe-66-24-56-78.stny.res.rr.com [66.24.56.78]) (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 5044E2081C; Fri, 9 Nov 2018 18:42:43 +0000 (UTC) Date: Fri, 9 Nov 2018 13:42:41 -0500 From: Steven Rostedt To: Josh Poimboeuf Cc: Andy Lutomirski , Ingo Molnar , LKML , X86 ML , Ard Biesheuvel , Peter Zijlstra , Thomas Gleixner , Linus Torvalds , Masami Hiramatsu , Jason Baron , Jiri Kosina , David Laight , Borislav Petkov Subject: Re: [PATCH RFC 0/3] Static calls Message-ID: <20181109134241.5f4ce3be@gandalf.local.home> In-Reply-To: <20181109164137.5cngbfrkm4ihj4ra@treble> References: <20181109072811.GB86700@gmail.com> <20181109152139.zig45f6gp24btfbc@treble> <20181109164137.5cngbfrkm4ihj4ra@treble> X-Mailer: Claws Mail 3.16.0 (GTK+ 2.24.32; x86_64-pc-linux-gnu) MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, 9 Nov 2018 10:41:37 -0600 Josh Poimboeuf wrote: > On Fri, Nov 09, 2018 at 09:21:39AM -0600, Josh Poimboeuf wrote: > > On Fri, Nov 09, 2018 at 07:16:17AM -0800, Andy Lutomirski wrote: > > > On Thu, Nov 8, 2018 at 11:28 PM Ingo Molnar wrote: > > > > > > > > > > > > All other usecases are bonus, but it would certainly be interesting to > > > > investigate the impact of using these APIs for tracing: that too is a > > > > feature enabled everywhere but utilized only by a small fraction of Linux > > > > users - so literally every single cycle or instruction saved or hot-path > > > > shortened is a major win. > > > > > > For tracing, we'd want static_call_set_to_nop() or something like that, right? > > > > Are we talking about tracepoints? Or ftrace? > > Since ftrace changes calls to nops, and vice versa, I assume you meant > ftrace. I don't think ftrace is a good candidate for this, as it's > inherently more flexible than this API would reasonably allow. > Not sure what Andy was talking about, but I'm currently implementing tracepoints to use this, as tracepoints use indirect calls, and are a prime candidate for static calls, as I showed in my original RFC of this feature. -- Steve