Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751291AbaDZHMV (ORCPT ); Sat, 26 Apr 2014 03:12:21 -0400 Received: from mail-ee0-f53.google.com ([74.125.83.53]:59327 "EHLO mail-ee0-f53.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750715AbaDZHMU (ORCPT ); Sat, 26 Apr 2014 03:12:20 -0400 Date: Sat, 26 Apr 2014 09:12:14 +0200 From: Ingo Molnar To: Masami Hiramatsu 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 Message-ID: <20140426071214.GA2374@gmail.com> 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> <535A2E41.40005@hitachi.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <535A2E41.40005@hitachi.com> User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org * Masami Hiramatsu wrote: > (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? It's more about the mental picture about how kprobes works. The fewer binary state flags, the better. Thanks, Ingo -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/