Re: [Xen-devel] [PATCH] xen: blkif.h: document linux xen-block multi-page ring implementation

[David Vrabel <david.vrabel@xxxxxxxxxx>]

On 15/05/15 11:39, Bob Liu wrote:
> 
> On 05/15/2015 05:51 PM, David Vrabel wrote:
>> On 12/05/15 11:58, Bob Liu wrote:
>>> After commit 1b1586eeeb8c ("xenbus_client: Extend interface to
>>> support multi-page ring"), Linux xenbus driver can support multi-page ring.
>>>
>>> Based on this interface, we got some impressive improvements by using 
>>> multi-page
>>> ring in xen-block driver. If using 64 pages as the ring, the IOPS increased
>>> about 15 times for the throughput testing.
>>>
>>> The Linux implementation reuses two 'DEPRECATED' nodes('max-ring-pages' and
>>> 'num-ring-pages), so that nothing would be broken.
>>> Also removed the power of 2 limit and updated the default/max value 
>>> accordingly.
>>
>> You can't drop the power of 2 restriction as there may be frontends that
>> support this old option (from before it was deprecated) and these may
>> not support non-powers of 2.
>>
> 
> After take a closer look I think we can fully reuse the current protocol which
> only uses 'ring-page-order' and 'max-ring-page-order'.
> And leave 'max-ring-pages' and 'num-ring-pages' to DEPRECATED.
> 
> In conclusion, the blkif.h don't need to be modified and I'll update Linux
> implementation to use 'ring-page-order' and 'max-ring-page-order' too.
> What do you think? Thank you!

This sounds fine.

David

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