Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1759074AbZCPMmy (ORCPT ); Mon, 16 Mar 2009 08:42:54 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1758979AbZCPMmk (ORCPT ); Mon, 16 Mar 2009 08:42:40 -0400 Received: from mail-qy0-f122.google.com ([209.85.221.122]:48306 "EHLO mail-qy0-f122.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1758514AbZCPMmi (ORCPT ); Mon, 16 Mar 2009 08:42:38 -0400 DomainKey-Signature: a=rsa-sha1; c=nofws; d=gmail.com; s=gamma; h=date:from:to:cc:subject:message-id:references:mime-version :content-type:content-disposition:in-reply-to:user-agent; b=FX9Njf76t8H97VH4o/4F7/P+zB0cX0mtH+XUFfLHm3Gk3LA8IE+H7+g7Lh39YTOZG9 gZT0Mt9YVELdLDtLgqF0MVJKAiY8/oQa1sS7U5Z1etQv4y/gD8tjAF0DJ6SXJ80dXK+V +AxA1rQnIaUth7EmzjBjeQUk3c04MSQxW3FMI= Date: Mon, 16 Mar 2009 13:42:30 +0100 From: Frederic Weisbecker To: mingo@redhat.com, hpa@zytor.com, linux-kernel@vger.kernel.org, srostedt@redhat.com, tglx@linutronix.de, laijs@cn.fujitsu.com, mingo@elte.hu Cc: linux-tip-commits@vger.kernel.org Subject: Re: [tip:tracing/ftrace] ftrace: remove struct list_head from struct dyn_ftrace Message-ID: <20090316124229.GB5096@nowhere> References: <49BA2C9F.8020009@cn.fujitsu.com> <20090316123607.GA5096@nowhere> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20090316123607.GA5096@nowhere> User-Agent: Mutt/1.5.18 (2008-05-17) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 3619 Lines: 112 On Mon, Mar 16, 2009 at 01:36:09PM +0100, Frederic Weisbecker wrote: > On Fri, Mar 13, 2009 at 10:39:36AM +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; > > + ftrace_new_addrs = rec; > > > But... you are overwritting all the ftrace flags infrastructure by > using it as a list pointer. > > This is breaking dynamic tracing. May be I'm wrong. May be I misunderstood this patch. But I don't understand how flags can be used at the same time as a pointer and as a flag value. > > > > 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; > > + 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-tip-commits" in > > the body of a message to majordomo@vger.kernel.org > > More majordomo info at http://vger.kernel.org/majordomo-info.html > -- 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/