linux-kernel - Vanilla-Kernel 3 - page allocation failure

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Message-ID: <4E9D53FF.7090609@profihost.ag>
Date:	Tue, 18 Oct 2011 12:25:03 +0200
From:	Philipp Herz - Profihost AG <p.herz@...fihost.ag>
To:	linux-kernel@...r.kernel.org
Subject: Vanilla-Kernel 3 - page allocation failure

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?

What is the magic behind the 'order' and 'mode'?

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
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