Subject: Re: [RFC] Hugetlb demotion for x86
From: Adam Litke <agl@us.ibm.com>
To: Christoph Lameter <christoph@engr.sgi.com>
Cc: linux-mm@kvack.kernel.org, linux-kernel@vger.kernel.org
In-Reply-To: <Pine.LNX.4.64.0605101633140.7639@schroedinger.engr.sgi.com>
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	 <Pine.LNX.4.64.0605101633140.7639@schroedinger.engr.sgi.com>
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Organization: IBM
Date: Thu, 11 May 2006 11:10:58 -0500
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On Wed, 2006-05-10 at 16:42 -0700, Christoph Lameter wrote:
> Seems that the code is not modifying x86 code but all code. 

Right.  It's definitely broken in that regard.  I sent it out in this
condition so the patch was small, easy to review, and my approach would
be easy to see.

> An app should be getting an out of memory error and not a SIGBUS when 
> running out of memory.
> 
> I thought we fixed the SIGBUS problems and were now reporting out of 
> memory? If there still is an issue then we better fix out of memory 
> handling. Provide a way for the app to trap OOM conditions?

Yes, the SIGBUS issues are "fixed".  Now the application is killed
directly via VM_FAULT_OOM so it is not possible to handle the fault from
userspace.  For my libhugetlbfs-based fallback approach, I needed to
patch the kernel so that SIGBUS was delivered to the process like in the
days of old.

-- 
Adam Litke - (agl at us.ibm.com)
IBM Linux Technology Center

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