From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752144Ab2LTAIS (ORCPT ); Wed, 19 Dec 2012 19:08:18 -0500 Received: from mail.linuxfoundation.org ([140.211.169.12]:44788 "EHLO mail.linuxfoundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751399Ab2LTAIH (ORCPT ); Wed, 19 Dec 2012 19:08:07 -0500 Date: Wed, 19 Dec 2012 16:08:05 -0800 From: Andrew Morton To: Johannes Weiner Cc: Rik van Riel , Michal Hocko , Mel Gorman , Hugh Dickins , Satoru Moriya , linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: Re: [patch 5/7] mm: vmscan: clean up get_scan_count() Message-Id: <20121219160805.658f724f.akpm@linux-foundation.org> In-Reply-To: <1355767957-4913-6-git-send-email-hannes@cmpxchg.org> References: <1355767957-4913-1-git-send-email-hannes@cmpxchg.org> <1355767957-4913-6-git-send-email-hannes@cmpxchg.org> X-Mailer: Sylpheed 3.0.2 (GTK+ 2.20.1; x86_64-pc-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, 17 Dec 2012 13:12:35 -0500 Johannes Weiner wrote: > Reclaim pressure balance between anon and file pages is calculated > through a tuple of numerators and a shared denominator. > > Exceptional cases that want to force-scan anon or file pages configure > the numerators and denominator such that one list is preferred, which > is not necessarily the most obvious way: > > fraction[0] = 1; > fraction[1] = 0; > denominator = 1; > goto out; > > Make this easier by making the force-scan cases explicit and use the > fractionals only in case they are calculated from reclaim history. > > And bring the variable declarations/definitions in order. > > ... > > + u64 fraction[2], uninitialized_var(denominator); Using uninitialized_var() puts Linus into rant mode. Unkindly, IMO: uninitialized_var() is documentarily useful and reduces bloat. There is a move afoot to replace it with int foo = 0; /* gcc */ To avoid getting ranted at we can do --- a/mm/vmscan.c~mm-vmscan-clean-up-get_scan_count-fix +++ a/mm/vmscan.c @@ -1658,7 +1658,8 @@ static void get_scan_count(struct lruvec unsigned long *nr) { struct zone_reclaim_stat *reclaim_stat = &lruvec->reclaim_stat; - u64 fraction[2], uninitialized_var(denominator); + u64 fraction[2]; + u64 denominator = 0; struct zone *zone = lruvec_zone(lruvec); unsigned long anon_prio, file_prio; enum scan_balance scan_balance; _ Which bloats the text by six bytes, but will force a nice div-by-zero if we ever hit that can't-happen path.