Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754584Ab0ARU6o (ORCPT ); Mon, 18 Jan 2010 15:58:44 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1754176Ab0ARU6m (ORCPT ); Mon, 18 Jan 2010 15:58:42 -0500 Received: from ogre.sisk.pl ([217.79.144.158]:50209 "EHLO ogre.sisk.pl" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753310Ab0ARU6l (ORCPT ); Mon, 18 Jan 2010 15:58:41 -0500 From: "Rafael J. Wysocki" To: Alan Stern Subject: Re: [linux-pm] [RFC][PATCH] PM: Force GFP_NOIO during suspend/resume (was: Re: Memory allocations in .suspend became very unreliable) Date: Mon, 18 Jan 2010 21:59:25 +0100 User-Agent: KMail/1.12.3 (Linux/2.6.33-rc4-rjw; KDE/4.3.3; x86_64; ; ) Cc: Oliver Neukum , LKML , "linux-mm" , linux-pm@lists.linux-foundation.org, Andrew Morton References: In-Reply-To: MIME-Version: 1.0 Content-Type: Text/Plain; charset="iso-8859-1" Content-Transfer-Encoding: 7bit Message-Id: <201001182159.25585.rjw@sisk.pl> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1316 Lines: 28 On Monday 18 January 2010, Alan Stern wrote: > On Mon, 18 Jan 2010, Oliver Neukum wrote: > > > Am Montag, 18. Januar 2010 00:00:23 schrieb Rafael J. Wysocki: > > > On Sunday 17 January 2010, Benjamin Herrenschmidt wrote: > > > > On Sun, 2010-01-17 at 14:27 +0100, Rafael J. Wysocki wrote: > > > ... > > > > However, it's hard to deal with the case of allocations that have > > > > already started waiting for IOs. It might be possible to have some VM > > > > hook to make them wakeup, re-evaluate the situation and get out of that > > > > code path but in any case it would be tricky. > > > > > > In the second version of the patch I used an rwsem that made us wait for these > > > allocations to complete before we changed gfp_allowed_mask. > > > > This will be a very, very hot semaphore. What's the impact on performance? > > Can it be replaced with something having lower overhead, such as SRCU? I'm not sure about that. In principle SRCU shouldn't be used if the reader can sleep unpredictably long and the memory allocation sutiation is one of these. Rafael -- 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/