From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754900Ab1JRLdA (ORCPT ); Tue, 18 Oct 2011 07:33:00 -0400 Received: from e24smtp05.br.ibm.com ([32.104.18.26]:33612 "EHLO e24smtp05.br.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752001Ab1JRLc7 (ORCPT ); Tue, 18 Oct 2011 07:32:59 -0400 Date: Tue, 18 Oct 2011 09:32:51 -0200 From: Thadeu Lima de Souza Cascardo To: Philipp Herz - Profihost AG Cc: linux-kernel@vger.kernel.org Subject: Re: Vanilla-Kernel 3 - page allocation failure Message-ID: <20111018113251.GA3782@oc1711230544.ibm.com> References: <4E9D53FF.7090609@profihost.ag> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <4E9D53FF.7090609@profihost.ag> User-Agent: Mutt/1.5.21 (2010-09-15) x-cbid: 11101811-2362-0000-0000-00000535FDC8 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Oct 18, 2011 at 12:25:03PM +0200, Philipp Herz - Profihost AG wrote: > After updating kernel (x86_64) to stable version 3 there are a few > messages appearing in the kernel log such as > > kworker/0:1: page allocation failure: order:1, mode:0x20 > mysql: page allocation failure: order:1, mode:0x20 > php5: page allocation failure: order:1, mode:0x20 > > Searching the net showed that these messages are known to occur since 2004. > > Some people were able to get rid of them by setting > /proc/sys/vm/min_free_kbytes to a high enough value. This does not > help in our case. > > > Is there a kernel comand line argument to avoid these messages? > > As of mm/page_alloc.c these messages are marked to be only warning > messages and would not appear if 'gpf_mask' was set to __GFP_NOWARN > in function warn_alloc_failed. > > How does this mask get set? Is it set by the "external" process > knocking at the memory manager? > Hello, Philipp. This happens when kernel tries to allocate memory, sometimes in response to some request by the user space, but also in other contexts. For example, an interrupt by a network driver may try to allocate memory. In this context, it will use GFP_ATOMIC as a mask, for example. The most usual flags in the kernel are GFP_KERNEL and GFP_ATOMIC. > What is the magic behind the 'order' and 'mode'? > The order is the binary log of the number of pages requested. So, order 1 allocations are 2 pages, order 4 would be 16 pages, for example. The mode is, in fact, gfp_flags. 0x20 is GFP_ATOMIC. This kind of allocation cannot do IO or access the filesystem. Also, it cannot wait for reclaim memory from cache. This warning is usually followed by some statistics about memory use in your system. Please post it to give more information about this situation. I have watched some of this happen when lots of cache is used by some filesystems. Perhaps, some tweaking of the vm sysctl options may help, but I can point any magic tweaking right now. Regards, Cascardo. > I'm not a subscriber, so please CC me a copy of messages related to > the subject. I'm not sure if I can help much by looking at the > inside of the kernel, but I will try my best to answer any questions > concerning this issue. > > Best regards, Philipp > -- > 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/