linux-kernel - Re: [Intel-IOMMU 02/10] Library routine for pre-allocat pool handling

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Message-ID: <Pine.LNX.4.64.0706081558090.4373@schroedinger.engr.sgi.com>
Date:	Fri, 8 Jun 2007 15:59:32 -0700 (PDT)
From:	Christoph Lameter <clameter@....com>
To:	Andi Kleen <ak@...e.de>
cc:	Andrew Morton <akpm@...ux-foundation.org>,
	"Keshavamurthy, Anil S" <anil.s.keshavamurthy@...el.com>,
	linux-kernel@...r.kernel.org, gregkh@...e.de, muli@...ibm.com,
	asit.k.mallick@...el.com, suresh.b.siddha@...el.com,
	arjan@...ux.intel.com, ashok.raj@...el.com, shaohua.li@...el.com,
	davem@...emloft.net
Subject: Re: [Intel-IOMMU 02/10] Library routine for pre-allocat pool handling

On Sat, 9 Jun 2007, Andi Kleen wrote:

> > Why was it not allowed? Because interrupts are disabled?
> 
> Allocating memory during page out under low memory could 
> lead to deadlocks. That is because Linux used to make no attempt
> to limit dirty pages for anonymous mappings and then you could
> end up with most of your memory dirty and not enough 
> memory cleanable for page out and then when page out 
> needs more memory you could be dead.
> 
> [yes that implies that mmap over NFS was always broken]

Right. We got that fixed in 2.6.19.

> Now there is a anon dirty limit since a few releases, but I'm not
> fully convinced it solves the problem completely.

A gut feeling or is there more?

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