Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1761705AbZCYPEU (ORCPT ); Wed, 25 Mar 2009 11:04:20 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1753327AbZCYPEK (ORCPT ); Wed, 25 Mar 2009 11:04:10 -0400 Received: from hrndva-omtalb.mail.rr.com ([71.74.56.122]:57504 "EHLO hrndva-omtalb.mail.rr.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752920AbZCYPEJ (ORCPT ); Wed, 25 Mar 2009 11:04:09 -0400 Date: Wed, 25 Mar 2009 11:04:06 -0400 (EDT) From: Steven Rostedt X-X-Sender: rostedt@gandalf.stny.rr.com To: Pekka Enberg 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 Subject: Re: [PATCH 2/5] mm: remove unlikly NULL from kfree In-Reply-To: <1237993145.30175.34.camel@penberg-laptop> Message-ID: 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> <1237993145.30175.34.camel@penberg-laptop> User-Agent: Alpine 2.00 (DEB 1167 2008-08-23) MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2032 Lines: 50 On Wed, 25 Mar 2009, Pekka Enberg wrote: > 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? I think it was Christoph Lameter (good you Cc'd him) told me that anything less that 99% is not worthy of a (un)likely macro. I honestly don't know. -- Steve -- 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/