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

[Roger Pau MonnÃ]

On 28/02/13 12:35, Jan Beulich wrote:
>>>> On 28.02.13 at 12:25, Roger Pau MonnÃ<roger.pau@xxxxxxxxxx> wrote:
>> This is the expanded graph that also contains indirect descriptors
>> without persistent grants:
>>
>> http://xenbits.xen.org/people/royger/plot_indirect_nopers.png 
> 
> Thanks. Interesting - this suggests an unexpectedly high hit rate.

This graph is using the default values, so we are persistently mapping
1024 grants of the possible 2080 that could be used by blkfront ((64
segments + 1 indirect gref) * 32 = 2080).

blkfront stores grants using a stack, so it should try to reuse the same
grants as much as possible. On the other hand, blkback cleans unused
grants periodically, to try to have the most commonly used blkfront
grants mapped.

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