From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752890AbaDYJnm (ORCPT ); Fri, 25 Apr 2014 05:43:42 -0400 Received: from mail9.hitachi.co.jp ([133.145.228.44]:38941 "EHLO mail9.hitachi.co.jp" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750719AbaDYJng (ORCPT ); Fri, 25 Apr 2014 05:43:36 -0400 Message-ID: <535A2E41.40005@hitachi.com> Date: Fri, 25 Apr 2014 18:43:29 +0900 From: Masami Hiramatsu Organization: Hitachi, Ltd., Japan User-Agent: Mozilla/5.0 (Windows NT 6.1; WOW64; rv:13.0) Gecko/20120614 Thunderbird/13.0.1 MIME-Version: 1.0 To: Ingo Molnar Cc: linux-kernel@vger.kernel.org, Andi Kleen , Ananth N Mavinakayanahalli , Sandeepa Prabhu , Frederic Weisbecker , x86@kernel.org, Steven Rostedt , fche@redhat.com, mingo@redhat.com, systemtap@sourceware.org, "H. Peter Anvin" , Thomas Gleixner Subject: Re: Re: [PATCH -tip v9 25/26] kprobes: Introduce kprobe cache to reduce cache misshits References: <20140417081636.26341.87858.stgit@ltc230.yrl.intra.hitachi.co.jp> <20140417081931.26341.47154.stgit@ltc230.yrl.intra.hitachi.co.jp> <20140424090134.GC7768@gmail.com> <5358F7A3.1000108@hitachi.com> <20140425082056.GB24829@gmail.com> In-Reply-To: <20140425082056.GB24829@gmail.com> Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org (2014/04/25 17:20), Ingo Molnar wrote: > > * Masami Hiramatsu wrote: > >>> So I don't think this should be a Kconfig entry, just enable it >>> unconditionally. That will further simplify the code. >> >> Hmm, it consumes some amount of memory (36KB/core) just for the case >> of several thousand of kprobes. On enterprise servers and desktop >> it's OK, no problem. But I think, some embedded systems with small >> resources will not want that. [...] > > They'll just disable kprobes in general. No, I'd like to provide kprobes (and dynamic events) to them (including me) for debugging and dynamic monitoring, instead of modifying code for adding events on their kernel. To solve some specific issues, specific events (not generic events) are required. Making local patches to add such events is an option, but it increases maintenance cost for rebasing. It is better to pay cost to maintain this kconfig on upstream as the maintainer for me instead of paying such ugly local cost. :( Anyway, this option is not easy for beginners, I think it should be defined with "if EXPERT" option and make it enabled by default. > Really, at this point complexity is our main concern. Agreed about complexity issue. However, even if we remove the Kconfig, we can just save 6 lines of the code, and one #ifdef block. Can that really solve the complexity problem? Thank you, -- Masami HIRAMATSU Software Platform Research Dept. Linux Technology Research Center Hitachi, Ltd., Yokohama Research Laboratory E-mail: masami.hiramatsu.pt@hitachi.com