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

[Bob Liu <bob.liu@xxxxxxxxxx>]

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!

Regards,
-Bob

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