Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1761626AbZCYO7V (ORCPT ); Wed, 25 Mar 2009 10:59:21 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1753291AbZCYO7K (ORCPT ); Wed, 25 Mar 2009 10:59:10 -0400 Received: from courier.cs.helsinki.fi ([128.214.9.1]:54750 "EHLO mail.cs.helsinki.fi" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752811AbZCYO7J (ORCPT ); Wed, 25 Mar 2009 10:59:09 -0400 Subject: Re: [PATCH 2/5] mm: remove unlikly NULL from kfree From: Pekka Enberg To: Steven Rostedt Cc: Hua Zhong , linux-kernel@vger.kernel.org, Ingo Molnar , Andrew Morton , Thomas Gleixner , Peter Zijlstra , Roland McGrath , Nick Piggin , Steven Rostedt , Christoph Lameter , Matt Mackall , Al Viro In-Reply-To: References: <20090325051920.406564281@goodmis.org> <20090325052023.071564146@goodmis.org> <84144f020903250034j24e1782bt5f73809b9349346c@mail.gmail.com> <009101c9ad20$1ae231c0$50a69540$@com> <1237968394.30175.12.camel@penberg-laptop> <84144f020903250651o13c723cgf64643091459a5ac@mail.gmail.com> Date: Wed, 25 Mar 2009 16:59:05 +0200 Message-Id: <1237993145.30175.34.camel@penberg-laptop> Mime-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Transfer-Encoding: 7bit X-Mailer: Evolution 2.22.3.1 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1769 Lines: 42 Hi Steven, On Wed, 25 Mar 2009, Pekka Enberg wrote: > > OK, so according to Steven, audit_syscall_exit() is one such call-site > > that shows up in the traces. I don't really understand what's going on > > there but if it is sane, maybe that warrants the removal of unlikely() > > from kfree(). Hmm? On Wed, 2009-03-25 at 10:47 -0400, Steven Rostedt wrote: > After disabling AUDIT_SYSCALLS I have this: > > # cat /debug/tracing/trace | sort -u > > record_nulls: ptr=(null) (ext3_get_acl+0x1e0/0x3f0 [ext3]) > record_nulls: ptr=(null) (free_bitmap+0x29/0x70) > record_nulls: ptr=(null) (free_tty_struct+0x1d/0x40) > record_nulls: ptr=(null) (ftrace_graph_exit_task+0x1e/0x20) > record_nulls: ptr=(null) (inet_sock_destruct+0x1cb/0x2a0) > record_nulls: ptr=(null) (ip_cork_release+0x24/0x50) > record_nulls: ptr=(null) (keyctl_join_session_keyring+0x5a/0x70) > record_nulls: ptr=(null) (key_user_lookup+0x183/0x220) > record_nulls: ptr=(null) (kobject_set_name_vargs+0x43/0x50) > record_nulls: ptr=(null) (netlink_release+0x1a4/0x2f0) > record_nulls: ptr=(null) (release_sysfs_dirent+0x20/0xc0) > record_nulls: ptr=(null) (sysfs_open_file+0x1c8/0x3e0) > record_nulls: ptr=(null) (tty_write+0x16a/0x290) > > I added a hook to only record when NULL is passed into kfree. > > Also note, that after disabling AUDIT_SYSCALLS I now only have roughly 7% > NULL hit rate. Still, unlikely is probably not a benefit here. Thanks for doing this. Do you mean that 93% hit ratio is not enough to be a performance gain? Pekka -- 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/