From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (qmail 13121 invoked by alias); 20 Dec 2013 09:31:45 -0000 Mailing-List: contact systemtap-help@sourceware.org; run by ezmlm Precedence: bulk List-Id: List-Subscribe: List-Post: List-Help: , Sender: systemtap-owner@sourceware.org Received: (qmail 13111 invoked by uid 89); 20 Dec 2013 09:31:45 -0000 Authentication-Results: sourceware.org; auth=none X-Virus-Found: No X-Spam-SWARE-Status: No, score=-1.8 required=5.0 tests=AWL,BAYES_00,RCVD_IN_DNSWL_LOW,SPF_PASS autolearn=ham version=3.3.2 X-HELO: mail9.hitachi.co.jp Received: from mail9.hitachi.co.jp (HELO mail9.hitachi.co.jp) (133.145.228.44) by sourceware.org (qpsmtpd/0.93/v0.84-503-g423c35a) with ESMTP; Fri, 20 Dec 2013 09:31:44 +0000 Received: from mlsv8.hitachi.co.jp (unknown [133.144.234.166]) by mail9.hitachi.co.jp (Postfix) with ESMTP id 8783537C95; Fri, 20 Dec 2013 18:31:42 +0900 (JST) Received: from mfilter05.hitachi.co.jp by mlsv8.hitachi.co.jp (8.13.1/8.13.1) id rBK9VgxH004193; Fri, 20 Dec 2013 18:31:42 +0900 Received: from vshuts02.hitachi.co.jp (vshuts02.hitachi.co.jp [10.201.6.84]) by mfilter05.hitachi.co.jp (Switch-3.3.4/Switch-3.3.4) with ESMTP id rBK9Vdeq029042; Fri, 20 Dec 2013 18:31:41 +0900 Received: from gxml20a.ad.clb.hitachi.co.jp (unknown [158.213.157.160]) by vshuts02.hitachi.co.jp (Postfix) with ESMTP id 53B51490062; Fri, 20 Dec 2013 18:31:41 +0900 (JST) Received: from [10.198.212.163] by gxml20a.ad.clb.hitachi.co.jp (Switch-3.1.10/Switch-3.1.9) id 5BK91V4FJ000043F0; Fri, 20 Dec 2013 18:31:40 +0900 Message-ID: <52B40E79.8040701@hitachi.com> Date: Fri, 20 Dec 2013 09:31:00 -0000 From: Masami Hiramatsu User-Agent: Mozilla/5.0 (Windows NT 5.2; rv:13.0) Gecko/20120614 Thunderbird/13.0.1 MIME-Version: 1.0 To: Ingo Molnar Cc: "Frank Ch. Eigler" , linux-arch@vger.kernel.org, Ananth N Mavinakayanahalli , Sandeepa Prabhu , x86@kernel.org, lkml , "Steven Rostedt (Red Hat)" , systemtap@sourceware.org, "David S. Miller" Subject: Re: [PATCH -tip v6 00/22] kprobes: introduce NOKPROBE_SYMBOL(), cleanup and fixes crash bugs References: <20131219090353.14309.15496.stgit@kbuild-fedora.novalocal> <52B3C5E6.2040802@hitachi.com> <20131220082056.GA15934@gmail.com> In-Reply-To: <20131220082056.GA15934@gmail.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-IsSubscribed: yes X-SW-Source: 2013-q4/txt/msg00461.txt.bz2 (2013/12/20 17:20), Ingo Molnar wrote: > > * Masami Hiramatsu wrote: > >>> But a closer look indicates that the insertion of kprobes is >>> taking about three (!!) orders of magnitude longer than before, as >>> judged by the rate of increase of 'wc -l >>> /sys/kernel/debug/kprobes/list'. >> >> Right, because kprobes are not designed for thousands of probes. > > Then this needs to be fixed, because right now this bug is making it > near impossible to properly test kprobes robustness. > > For example a hash table (hashed by probe address) could be used in > addition to the list, to speed up basic operations. kprobe itself is already using hlist (6bits hash table). Maybe we'd better expand the table bits. However, the iteration of the list on debugfs is just doing seq_printf()s. I'm not exactly sure what Frank complaints about... I recommend Frank to use perf record and perf annotation to clarify which part caused that slow down. Thank you, -- Masami HIRAMATSU IT Management Research Dept. Linux Technology Center Hitachi, Ltd., Yokohama Research Laboratory E-mail: masami.hiramatsu.pt@hitachi.com