Re: [Intel IOMMU 06/10] Avoid memory allocation failures in dma map api calls

[Peter Zijlstra <peterz@infradead.org>]

On Wed, 2007-06-20 at 23:37 -0700, Keshavamurthy, Anil S wrote:
> On Thu, Jun 21, 2007 at 08:29:34AM +0200, Peter Zijlstra wrote:
> > On Wed, 2007-06-20 at 23:11 -0700, Arjan van de Ven wrote:
> > > Peter Zijlstra wrote:
> > Also, the other iommu code you pointed me to, was happy to fail, it did
> > not attempt to use the emergency reserves.
> 
> Is the same behavior acceptable here?

I would say it is. Failure is a part of life.

If you have a (small) mempool with 16 pages or so, that should give you
plenty megabytes of io-space to get out of a tight spot. That is, you
can queue many pages with that. If it is depleted you know you have at
least that many pages outstanding. So failing will just delay the next
pages.

Throughput is not a key issue when that low on memory, a guarantee of
progress is.


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