Re: [Xen-devel] [PATCH RFC] xenbus_client: extend interface to suppurt multi-page ring

[Wei Liu <liuw@xxxxxxxxx>]

On Tue, Aug 20, 2013 at 6:11 PM, Konrad Rzeszutek Wilk
<konrad.wilk@xxxxxxxxxx> wrote:
> On Thu, May 30, 2013 at 03:09:12PM +0100, Wei Liu wrote:
>> On Thu, May 30, 2013 at 03:06:00PM +0100, Wei Liu wrote:
>> > Originally Xen PV drivers only use single-page ring to pass along
>> > information. This might limit the throughput between frontend and
>> > backend as they can easily run out of ring slots if hardware is fast.
>> >
>> > The patch extends Xenbus driver to support multi-page ring, which in
>> > general should improve throughput. Changes to various frontend / backend
>> > to adapt to the new interface are also included.
>> >
>> > Affected Xen drivers:
>> > * blkfront/back
>> > * netfront/back
>> > * pcifront/back
>> >
>> > The interface is documented, as before, in xenbus_client.c.
>> >
>>
>> Please note that this patch won't apply cleanly on upstream kernel as it
>> relies on some patches that are not in tree.
>
> OK.
>>
>> I mainly want to collect views on the interface.  Also in the HVM case I
>> use vmap, I would like to know if I get it right.
>
> This patches looks familiar that I had seen some time ago (maybe I even
> backported it for PV?). Anyhow the PV part looks OK.
>
> The HVM - I don't see why we cannot do vmap. The nature of the ring is that
> it stays mapped for a very long time - so using vmap is OK. That is, the
> issues with vmap is that it takes a bit to setup and teardown - and that
> is OK with us.
>
> If you would like to rebase it on top of v3.11-rc5 and repost it I don't
> see why we can't have it for v3.12. David, Boris?
>

I think the above implementation has a problem in the HVM case, but I
cannot recall what. :-(

If you're generally happy with the idea, I can polish this patch and
target it for 3.12.

Wei.

>>
>>
>> Thanks
>> Wei.
>>
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>
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