From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail191.messagelabs.com (mail191.messagelabs.com [216.82.242.19]) by kanga.kvack.org (Postfix) with SMTP id B341E6B0088 for ; Mon, 18 Jan 2010 15:55:43 -0500 (EST) From: "Rafael J. Wysocki" Subject: Re: [RFC][PATCH] PM: Force GFP_NOIO during suspend/resume (was: Re: [linux-pm] Memory allocations in .suspend became very unreliable) Date: Mon, 18 Jan 2010 21:56:26 +0100 References: <1263549544.3112.10.camel@maxim-laptop> <201001180000.23376.rjw@sisk.pl> <201001180853.31446.oliver@neukum.org> In-Reply-To: <201001180853.31446.oliver@neukum.org> MIME-Version: 1.0 Content-Type: Text/Plain; charset="utf-8" Content-Transfer-Encoding: 7bit Message-Id: <201001182156.26878.rjw@sisk.pl> Sender: owner-linux-mm@kvack.org To: Oliver Neukum Cc: Benjamin Herrenschmidt , Maxim Levitsky , linux-pm@lists.linux-foundation.org, LKML , linux-mm , Andrew Morton List-ID: On Monday 18 January 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? rwsems are highly optimized AFAICT, but this is a good question of course. I have no data at the moment. Rafael -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org