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Re: [Xen-devel] [PATCH 0/6] grantable and address conversion patches

To: Keir Fraser <Keir.Fraser@xxxxxxxxxxxx>
Subject: Re: [Xen-devel] [PATCH 0/6] grantable and address conversion patches
From: Keir Fraser <Keir.Fraser@xxxxxxxxxxxx>
Date: Mon, 10 Apr 2006 10:00:38 +0100
Cc: Isaku Yamahata <yamahata@xxxxxxxxxxxxx>, xen-devel@xxxxxxxxxxxxxxxxxxx
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On 10 Apr 2006, at 09:54, Keir Fraser wrote:

2/6: This is a poor fix. Either we should make the ring size fixed (e.g., 4kB) rather than architectural page-sized, or grants should be dynamically allocated in netfront rather than statically allocated. This was done quite some time ago for blkfront, and would be the preferred (although more difficult) fix here.

Actually, another option that might be easier that dynamic grant allocation, but less restrictive that reducing the size of the rings on ia64, would be to modify netfront to queue only up to 256 requests simultaneously on any ring, regardless of the actual ring size. Then you'd only need to allocate 256 grants per ring, as x86, and the bigger issue (dynamic allocation of grants) can be fixed later. At that point we can lift the restriction of 256 requests per ring without having to change the public interface at all (unlike if we'd reduced the advertised ring size for ia64).

 -- Keir

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