From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756177Ab2BUWhW (ORCPT ); Tue, 21 Feb 2012 17:37:22 -0500 Received: from mail-pz0-f46.google.com ([209.85.210.46]:46711 "EHLO mail-pz0-f46.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755321Ab2BUWhV (ORCPT ); Tue, 21 Feb 2012 17:37:21 -0500 Authentication-Results: mr.google.com; spf=pass (google.com: domain of hughd@google.com designates 10.68.217.42 as permitted sender) smtp.mail=hughd@google.com; dkim=pass header.i=hughd@google.com Date: Tue, 21 Feb 2012 14:36:56 -0800 (PST) From: Hugh Dickins X-X-Sender: hugh@eggly.anvils To: KAMEZAWA Hiroyuki cc: Andrew Morton , Konstantin Khlebnikov , Johannes Weiner , Ying Han , linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH 5/10] mm/memcg: introduce page_relock_lruvec In-Reply-To: <20120221173859.f57d00f5.kamezawa.hiroyu@jp.fujitsu.com> Message-ID: References: <20120221173859.f57d00f5.kamezawa.hiroyu@jp.fujitsu.com> User-Agent: Alpine 2.00 (LSU 1167 2008-08-23) MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, 21 Feb 2012, KAMEZAWA Hiroyuki wrote: > > No perforamce impact by replacing spin_lock_irq()/spin_unlock_irq() to > spin_lock_irqsave() and spin_unlock_irqrestore() ? None that I noticed - but that is not at all a reassuring answer! It worries me a little. I think it would make more or less difference on different architectures, and I forget where x86 stands there - one of the more or the less affected? Worth branches down inside page_relock_lruvec()? It's also unfortunate to be "losing" the information of where _irq is needed and where _irqsave (but not much gets lost with git). It's something that can be fixed - and I think Konstantin's version already keeps the variants: I just didn't want to get confused by them, while focussing on the locking details. Hugh