Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753093Ab1BCVQU (ORCPT ); Thu, 3 Feb 2011 16:16:20 -0500 Received: from mail-ey0-f174.google.com ([209.85.215.174]:62873 "EHLO mail-ey0-f174.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752799Ab1BCVQT convert rfc822-to-8bit (ORCPT ); Thu, 3 Feb 2011 16:16:19 -0500 DomainKey-Signature: a=rsa-sha1; c=nofws; d=gmail.com; s=gamma; h=mime-version:in-reply-to:references:date:message-id:subject:from:to :cc:content-type:content-transfer-encoding; b=Fg/42CZW3lyhMG/ndVaakcmrgjwgwfFZob0UlvX1YsnSRqer3gPuMdaUnMI73uY/Ad 9udLbWO96WQ2a30tAjWOtr192Jbk28S+BuKX7VSPNnw4P7dFteExgerPkhGSHyu3PfYQ q5oGXXi1fVsgAC2BDI2QCDtBx/Amf5hPn5jVg= MIME-Version: 1.0 In-Reply-To: <20110203190612.GL5843@random.random> References: <20110201154947.GX16981@random.random> <20110203132407.GF11958@csn.ul.ie> <20110203190612.GL5843@random.random> Date: Thu, 3 Feb 2011 22:16:17 +0100 Message-ID: Subject: Re: khugepaged: gets stuck when writing to USB flash, 2.6.38-rc2 From: =?ISO-8859-2?Q?Jind=F8ich_Makovi=E8ka?= To: Andrea Arcangeli Cc: Mel Gorman , linux-kernel@vger.kernel.org, Andrew Morton Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8BIT Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1609 Lines: 34 On Thu, Feb 3, 2011 at 20:06, Andrea Arcangeli wrote: > On Thu, Feb 03, 2011 at 01:24:08PM +0000, Mel Gorman wrote: >> This is very likely. Compaction calls into migration which will wait on >> dirty pages after a time. With a large number of dirty pages backed by a >> slow drive such as a USB stick, it could be getting stalled there for a >> long period of time. >> >> Whether migration sleeps or not can be controlled by the sync parameter >> passed into try_to_compact_memory which could be always forced to false >> if GFP_NO_KSWAPD? > > I would expect that to hide any regression we could have because of > more dirty cache in the system, yes. > > However Jindřich reported not being able to reproduce anything anymore > in -rc3, so I'm unsure if we should make that change anymore. I asked > to try again cause it should too easy that got fixed magically I tried again and reproduced with -rc3 too, sorry for misinformation. I also tried echo never > /sys/kernel/mm/transparent_hugepage/defrag , and it seems preventing the system freeze, but still the copying itself sometimes comes to almost complete stop (GkrellM shows short spikes of tens of kB/s on the USB /dev/sdX). In this case, khugepaged is also in DN. I still didn't observe this problem when disabling THP completely by echo never > enabled . -- Jindrich Makovicka -- 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/