Messages in this thread | | | Date | Wed, 2 Nov 2011 03:25:44 -0400 | From | Christoph Hellwig <> | Subject | Re: [PATCH 2/5] virtio: support unlocked queue kick |
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On Wed, Nov 02, 2011 at 01:49:36PM +1030, Rusty Russell wrote: > I thought it was still a WIP?
The whole series - yes. This patch (and the serial number rewrite): no - these are pretty much rock solid.
> Since the problem is contention on the lock inside the block layer, the > simplest solution is to have a separate lock to protect the virtqueue.
As long as we still use a ->request_fn based driver that is not going to buy us anything, in fact it's going to make things worse. ->request_fn based drivers always have the queue lock held over the invocation of ->request_fn anyway, and then need it around the call to __blk_end_request_all. So you might minimally reduce contention time, but skyrocket the number of lock acquisations when separating them without changes to the block layer.
With the ->make_request_fn based driver vlkb->lock does't protect anything but the virtuequeue anyway, but not having to take it over the wakeup there is a) done easily and b) neatly fits the model.
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