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

On Thu, Nov 15, 2012 at 4:38 PM, ANNIE LI <annie.li@xxxxxxxxxx> wrote:

On 2012-11-15 15:40, Pasi KÃrkkÃinen wrote:

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, Â Â ÂAvg, Â Â Min, Â Â Max
Â1, Â15106.4, Â15106.4, 15106.36, 15106.36
Â2, Â13052.7, Â6526.34, Â6261.81, Â6790.86
Â3, Â12675.1, Â6337.53, Â6220.24, Â6454.83
Â4, Â13194, Â6596.98, Â6274.70, Â6919.25

Following are result of without persistent patch

Guests, Sum, Â Â Avg, Â ÂMin, Â Â Â ÂMax
Â1, Â10864.1, Â10864.1, 10864.10, 10864.10
Â2, Â10898.5, Â5449.24, Â4862.08, Â6036.40
Â3, Â10734.5, Â5367.26, Â5261.43, Â5473.08
Â4, Â10924, Â Â5461.99, Â5314.84, Â5609.14

Interesting results. Have you tested how good it is on a 10G nic, i.e. guest sending packets
through physical network to another host.

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