Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1758732AbZCMNRL (ORCPT ); Fri, 13 Mar 2009 09:17:11 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1754335AbZCMNQ4 (ORCPT ); Fri, 13 Mar 2009 09:16:56 -0400 Received: from mx2.redhat.com ([66.187.237.31]:48194 "EHLO mx2.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754240AbZCMNQz (ORCPT ); Fri, 13 Mar 2009 09:16:55 -0400 Subject: Re: [tip:tracing/ftrace] ftrace: remove struct list_head from struct dyn_ftrace From: Steven Rostedt To: mingo@redhat.com, hpa@zytor.com, linux-kernel@vger.kernel.org, tglx@linutronix.de, laijs@cn.fujitsu.com, mingo@elte.hu Cc: linux-tip-commits@vger.kernel.org In-Reply-To: References: <49BA2C9F.8020009@cn.fujitsu.com> Content-Type: text/plain Organization: Red Hat Date: Fri, 13 Mar 2009 09:16:30 -0400 Message-Id: <1236950190.11290.15.camel@localhost.localdomain> Mime-Version: 1.0 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 3330 Lines: 124 On Fri, 2009-03-13 at 10:39 +0000, Lai Jiangshan wrote: > Commit-ID: e94142a67f8bad494c593f0a07c9fc2fbec98c0e > Gitweb: http://git.kernel.org/tip/e94142a67f8bad494c593f0a07c9fc2fbec98c0e > Author: Lai Jiangshan > AuthorDate: Fri, 13 Mar 2009 17:51:27 +0800 > Commit: Ingo Molnar > CommitDate: Fri, 13 Mar 2009 11:36:20 +0100 > > ftrace: remove struct list_head from struct dyn_ftrace > Impact: save memory > > The struct dyn_ftrace table is very large, this patch will save > about 50%. > > Signed-off-by: Lai Jiangshan > Cc: Steven Rostedt > LKML-Reference: <49BA2C9F.8020009@cn.fujitsu.com> > Signed-off-by: Ingo Molnar > > > --- > include/linux/ftrace.h | 1 - > kernel/trace/ftrace.c | 14 ++++++++------ > 2 files changed, 8 insertions(+), 7 deletions(-) > > diff --git a/include/linux/ftrace.h b/include/linux/ftrace.h > index c146c10..9d598bb 100644 > --- a/include/linux/ftrace.h > +++ b/include/linux/ftrace.h > @@ -145,7 +145,6 @@ enum { > }; > > struct dyn_ftrace { > - struct list_head list; > unsigned long ip; /* address of mcount call-site */ > unsigned long flags; > struct dyn_arch_ftrace arch; > diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c > index bf78a4c..90d5729 100644 > --- a/kernel/trace/ftrace.c > +++ b/kernel/trace/ftrace.c > @@ -272,7 +272,7 @@ enum { > > static int ftrace_filtered; > > -static LIST_HEAD(ftrace_new_addrs); > +static struct dyn_ftrace *ftrace_new_addrs; > > static DEFINE_MUTEX(ftrace_regex_lock); > > @@ -409,8 +409,8 @@ ftrace_record_ip(unsigned long ip) > return NULL; > > rec->ip = ip; > - > - list_add(&rec->list, &ftrace_new_addrs); > + rec->flags = (unsigned long)ftrace_new_addrs; Lets not play games with pointers. If we are going to do this, make it into a union. struct dyn_arch_ftrace { unsigned long ip; union { unsigned long flags; struct dyn_arch_ftrace *next; } struct dyn_arch_ftrace arch; }; This way it is much clearer to what is going on. > + ftrace_new_addrs = rec; > > return rec; > } > @@ -716,19 +716,21 @@ unsigned long ftrace_update_tot_cnt; > > static int ftrace_update_code(struct module *mod) > { > - struct dyn_ftrace *p, *t; > + struct dyn_ftrace *p; > cycle_t start, stop; > > start = ftrace_now(raw_smp_processor_id()); > ftrace_update_cnt = 0; > > - list_for_each_entry_safe(p, t, &ftrace_new_addrs, list) { > + while (ftrace_new_addrs) { > > /* If something went wrong, bail without enabling anything */ > if (unlikely(ftrace_disabled)) > return -1; > > - list_del_init(&p->list); > + p = ftrace_new_addrs; > + ftrace_new_addrs = (struct dyn_ftrace *)p->flags; This confused me (and scared me) for a bit. Having a union would not have. Make the change to a union, and then you have my: Acked-by: Steven Rostedt Thanks, -- Steve > + p->flags = 0L; > > /* convert record (i.e, patch mcount-call with NOP) */ > if (ftrace_code_disable(mod, p)) { -- 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/