From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S933617AbaJ2Oim (ORCPT ); Wed, 29 Oct 2014 10:38:42 -0400 Received: from mail-qg0-f53.google.com ([209.85.192.53]:59456 "EHLO mail-qg0-f53.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932475AbaJ2Oil (ORCPT ); Wed, 29 Oct 2014 10:38:41 -0400 Date: Wed, 29 Oct 2014 10:38:38 -0400 From: Tejun Heo To: pang.xunlei@zte.com.cn Cc: linux-kernel@vger.kernel.org, Andrew Morton , Lai Jiangshan Subject: Re: [PATCH] idr: optimize ida_init() to avoid an extra memset Message-ID: <20141029143838.GC25226@htj.dyndns.org> References: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.23 (2014-03-12) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Oct 29, 2014 at 05:26:34PM +0800, pang.xunlei@zte.com.cn wrote: > The memset in ida_init() already handles idr, so there's some > redundancy in the following idr_init(). > > This patch removes the memset, and clears ida->free_bitmap instead. > > Signed-off-by: pang.xunlei > --- > lib/idr.c | 3 +-- > 1 file changed, 1 insertion(+), 2 deletions(-) > > diff --git a/lib/idr.c b/lib/idr.c > index e654aeb..bbe5779 100644 > --- a/lib/idr.c > +++ b/lib/idr.c > @@ -1141,8 +1141,7 @@ EXPORT_SYMBOL(ida_simple_remove); > */ > void ida_init(struct ida *ida) > { > - memset(ida, 0, sizeof(struct ida)); > idr_init(&ida->idr); > - > + ida->free_bitmap = NULL; I don't know. Does this matter? If this *really* matters, I'd much rather have memset(&ida->FIRST_FIELD, 0, sizeof(struct ida) - offset of FIRST_FIELD) to ensure that all fields get reset or implement an internal function like __idr_init_without_zeroing(); however, given the size of an idr and the low frequency of the operation, I'd prefer to just leave it as-is. Thanks. -- tejun