Subject: Re: [Xen-devel] [PATCH 0/4] Implement persistent grant in xen-netfront/netback

From: Roger Pau Monné <[email-masked]>
Date: Thu, 15 Nov 2012 11:56:17 +0100

On 15/11/12 09:38, ANNIE LI wrote:
> 
> 
> On 2012-11-15 15:40, Pasi Kärkkäinen wrote:
>> Hello,
>>
>> On Thu, Nov 15, 2012 at 03:03:07PM +0800, Annie Li wrote:
>>> This patch implements persistent grants for xen-netfront/netback. This
>>> mechanism maintains page pools in netback/netfront, these page pools is used to
>>> save grant pages which are mapped. This way improve performance which is wasted
>>> when doing grant operations.
>>>
>>> Current netback/netfront does map/unmap grant operations frequently when
>>> transmitting/receiving packets, and grant operations costs much cpu clock. In
>>> this patch, netfront/netback maps grant pages when needed and then saves them
>>> into a page pool for future use. All these pages will be unmapped when
>>> removing/releasing the net device.
>>>
>> Do you have performance numbers available already? with/without persistent grants?
> I have some simple netperf/netserver test result with/without persistent 
> grants,
> 
> Following is result of with persistent grant patch,
> 
> Guests, Sum,      Avg,     Min,     Max
>   1,  15106.4,  15106.4, 15106.36, 15106.36
>   2,  13052.7,  6526.34,  6261.81,  6790.86
>   3,  12675.1,  6337.53,  6220.24,  6454.83
>   4,  13194,  6596.98,  6274.70,  6919.25
> 
> 
> Following are result of without persistent patch
> 
> Guests, Sum,     Avg,    Min,        Max
>   1,  10864.1,  10864.1, 10864.10, 10864.10
>   2,  10898.5,  5449.24,  4862.08,  6036.40
>   3,  10734.5,  5367.26,  5261.43,  5473.08
>   4,  10924,    5461.99,  5314.84,  5609.14

In the block case, performance improvement is seen when using a large
number of guests, could you perform the same benchmark increasing the
number of guests to 15?