RE: [Xen-devel] RE: freezing when using GPLPV drivers (including Dom0)

["Ian Pratt" <Ian.Pratt@xxxxxxxxxxxxx>]

> I've never even heard of loop-ng... I just did a 'find' for any kernel
> module with 'loop' in the name and didn't see anything called
> 'loop-ng'... is it something I need to enable in the kernel config?

It's now part of device mapper, and called dm-loop. The key improvement
is that it's supposed to avoid dirtying unbounded amounts of memory and
then deadlocking. 

[However, this type of deadlock is fairly terminal -- I've never tried,
but I don't think 'sync' would unwedge it, so you may have a different
issue.]

> I just tried tap:aio but the DomU hung for ages after starting the
> restore... I'm just about to investigate.

Blktap certainly doesn't suffer from memory deadlock issues as it opens
the file O_DIRECT.

BTW: To my mind we should switch over from blktap to blktap2 soon.
Blktap2 isn't as mature yet, but its more aesthetically pleasing and has
equivalent performance. 

Ian

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