Re: [Intel-IOMMU 02/10] Library routine for pre-allocat poolhandling

From: Andrew Morton
Date: Mon Jun 11 2007 - 21:36:25 EST

On Mon, 11 Jun 2007 18:10:40 -0700 Arjan van de Ven <arjan@xxxxxxxxxxxxxxx> wrote:

> Andrew Morton wrote:
> >> Where as resource pool is exactly opposite of mempool, where each
> >> time it looks for an object in the pool and if it exist then we
> >> return that object else we try to get the memory for OS while
> >> scheduling the work to grow the pool objects. In fact, the work
> >> is schedule to grow the pool when the low threshold point is hit.
> >
> > I realise all that. But I'd have thought that the mempool approach is
> > actually better: use the page allocator and only deplete your reserve pool
> > when the page allocator fails.
> the problem with that is that if anything downstream from the iommu
> layer ALSO needs memory, we've now eaten up the last free page and
> things go splat.

If that happens, we still have the mempool reserve to fall back to.

I don't see why it is better to consume the reserves before going to the
page allocator instead of holding them, err, in reserve.

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