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Re: [Xen-devel] xenstored misaccounting resource limits

To: John Levon <levon@xxxxxxxxxxxxxxxxx>, <xen-devel@xxxxxxxxxxxxxxxxxxx>
Subject: Re: [Xen-devel] xenstored misaccounting resource limits
From: Keir Fraser <keir@xxxxxxxxxxxxx>
Date: Wed, 23 May 2007 09:20:59 +0100
Cc: max.zhen@xxxxxxx
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On 23/5/07 03:46, "John Levon" <levon@xxxxxxxxxxxxxxxxx> wrote:

> Currently xenstored does not account domain->nbentry when a transaction
> is aborted (either intentionally or via EAGAIN). We hit this case when
> adding a lot of disks to a domU: the limit is reached much earlier than
> expected, as a number of clashing transactions cause incorrect inflation
> of the value of ->nbentry.
> There's been a little discussion internally on the nicest way to fix
> this. My current suggestion is along the lines of:

The principle is clearly right, but domain_nbcount[] isn't a great idea
since the domain-id space is 16 bits (even though we do tend to pack domain
ids near zero where possible). Can we dynamically allocate the transaction
counts, or assign guaranteed packed identifiers, or store the counts within
the tdb file, or something like that?

 -- Keir

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