From mboxrd@z Thu Jan 1 00:00:00 1970 From: Ingo Molnar Subject: Re: [PATCH -tip v6 00/22] kprobes: introduce NOKPROBE_SYMBOL(), cleanup and fixes crash bugs Date: Sun, 9 Feb 2014 15:37:09 +0100 Message-ID: <20140209143709.GA31608@gmail.com> References: <20131219090353.14309.15496.stgit@kbuild-fedora.novalocal> <52B3C5E6.2040802@hitachi.com> <20131220082056.GA15934@gmail.com> <52B40E79.8040701@hitachi.com> <20131220104615.GA22609@gmail.com> <52E8E487.2090007@hitachi.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: List-Unsubscribe: List-Subscribe: List-Post: List-Help: , Sender: systemtap-owner@sourceware.org Content-Disposition: inline In-Reply-To: <52E8E487.2090007@hitachi.com> To: Masami Hiramatsu 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" List-Id: linux-arch.vger.kernel.org * Masami Hiramatsu wrote: > I guess the second reason is why the stap takes so long time to set > probes. stap tries to register kprobes without disabled flag, that > means we enables thousands of probes (overheads). > > So the similar thing happens when we enables events as below; > > # for i in /sys/kernel/debug/tracing/events/kprobes/* ; do date; echo 1 > $i; done > Wed Jan 29 10:44:50 UTC 2014 > ... > > I tried it and canceled after 4 min passed. It enabled about 17k > events and slowed down my system very much(I almost got hang check > timer). Ok, I guess that's the slowdown bug that Frank reported. > I think we should have some performance statistics (hit count?) and > if it goes over a threshold, we should stop enabling other events. That really feels like a hack. How about fixing the root cause? Does the enabling of all probes have to be so slow? Thanks, Ingo