Re: [Xen-devel] [PATCH RFC 00/12] xen-block: indirect descriptors

From: Roger Pau Monné
Date: Thu Feb 28 2013 - 06:25:34 EST

On 28/02/13 11:49, Jan Beulich wrote:
>>>> On 28.02.13 at 11:28, Roger Pau Monne <roger.pau@xxxxxxxxxx> wrote:
>> This series contains the initial implementation of indirect
>> descriptors for Linux blkback/blkfront.
>> Patches 1, 2, 3, 4 and 5 are bug fixes and minor optimizations.
>> Patch 6 contains a LRU implementation for blkback that will be needed
>> when using indirect descriptors (since we are no longer able to map
>> all possible grants blkfront might use).
> Considering this, ...
>> Patch 7 is an addition to the print stats function in blkback in order
>> to print information regarding persistent grant usage.
>> Patches 8, 9, 10 and 11 are preparatory work for indirect descriptors
>> implementation, mainly make blkback use dynamic memory and remove the
>> shared blkbk structure, so each blkback instance has it's own list of
>> free requests, pages, handles and so on.
>> Finally patch 12 contains the indirect descriptors implementation.
>> I've also pushed this series to the following git repository:
>> git:// xen-block-indirect
>> Performance benefit of this series can be seen in the following graph:
> ... would you happen to also have a comparison with using
> indirect descriptors but not persistent grants? IOW I'm
> wondering about the hit rate on the persistently mapped
> grants, especially when blkfront really saturates the added
> bandwidth.

This is the expanded graph that also contains indirect descriptors
without persistent grants:

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