From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754831AbZEXUb5 (ORCPT ); Sun, 24 May 2009 16:31:57 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1752035AbZEXUbu (ORCPT ); Sun, 24 May 2009 16:31:50 -0400 Received: from mail-fx0-f168.google.com ([209.85.220.168]:50074 "EHLO mail-fx0-f168.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752005AbZEXUbt (ORCPT ); Sun, 24 May 2009 16:31:49 -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=YWyrac0OZYp8TyssZSA+hbO8K5hX+Wt+F1ldvikQbdCyVTx8nyYxHsYjFm6SX7QEXI NoRfJOlfIGgBxmt7TzmQ5rFCxGmYykJA6USmHq/yVOwpURP2lZ42UiSkqU+OFvjAb1us n8ex2sszuT/9nCzByIa+HeHIHhg+nib1luG8c= Date: Sun, 24 May 2009 22:31:51 +0200 From: Frederic Weisbecker To: Li Zefan Cc: Ingo Molnar , Steven Rostedt , LKML Subject: Re: [PATCH] tracing/events: change the type of __str_loc_item to unsigned short Message-ID: <20090524203148.GA6471@nowhere> References: <4A14EDB6.2050507@cn.fujitsu.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <4A14EDB6.2050507@cn.fujitsu.com> 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 On Thu, May 21, 2009 at 01:59:18PM +0800, Li Zefan wrote: > When defining a dynamic size string, we add __str_loc_##item to the > trace entry, and it stores the location of the actual string in > entry->_str_data[] > > 'unsigned short' should be sufficient to store this information, thus > we save 2 bytes per dyn-size string in the ring buffer. > > [ Impact: reduce memory occupied by dyn-size strings in ring buffer ] > > Signed-off-by: Li Zefan > --- > include/trace/ftrace.h | 2 +- > 1 files changed, 1 insertions(+), 1 deletions(-) > > diff --git a/include/trace/ftrace.h b/include/trace/ftrace.h > index edb02bc..b5ff2e8 100644 > --- a/include/trace/ftrace.h > +++ b/include/trace/ftrace.h > @@ -25,7 +25,7 @@ > #define __field(type, item) type item; > > #undef __string > -#define __string(item, src) int __str_loc_##item; > +#define __string(item, src) unsigned short __str_loc_##item; > > #undef TP_STRUCT__entry > #define TP_STRUCT__entry(args...) args > -- 1.5.4.rc3 Yeah, a max length of about 32000 is sufficient, the filter engine is bounded to MAX_FILTER_STR_VAL anyway :) Acked-by: Frederic Weisbecker