From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754383Ab3LCRQO (ORCPT ); Tue, 3 Dec 2013 12:16:14 -0500 Received: from cantor2.suse.de ([195.135.220.15]:42745 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753466Ab3LCRQM (ORCPT ); Tue, 3 Dec 2013 12:16:12 -0500 Subject: [BUG] ftrace: support for SOFT_DISABLE to syscall events caused huge slowdown of ftrace startup test From: Petr Mladek To: Tom Zanussi , Steven Rostedt Cc: Jiri Kosina , linux-kernel@vger.kernel.org Content-Type: text/plain; charset="UTF-8" Date: Tue, 03 Dec 2013 18:16:09 +0100 Message-ID: <1386090969.1603.72.camel@pathway.suse.cz> Mime-Version: 1.0 X-Mailer: Evolution 2.28.2 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi, I tested my ftrace-related patches and enabled also the startup test: CONFIG_FTRACE_SELFTEST=y CONFIG_FTRACE_STARTUP_TEST=y On today's kernel/git/tip/tip.git, the boot "freezed" for 1 minute when doing "Testing event system syscalls". A bisect pointed finger to the commit d562aff93bfb530b099 (tracing: Add support for SOFT_DISABLE to syscall events). It seems that the culprit are the "synchronize_sched" calls added to "unreg_event_syscall_enter" and "unreg_event_syscall_exit" functions. They are called 2312 times during the boot here and are responsible for the delay. I wonder if it might cause slowdown also at runtime. I am going to look deeper into the code and eventually come up with a solution. But it might take some time. I am still newbie in the kernel development. Any hints or tips are welcome ;-) Best Regards, Petr