Re: [RFC PATCHv1 net-next] xen-netback: always fully coalesce guest Rx packets

[David Vrabel <david.vrabel@citrix.com>]

On 20/01/15 11:34, Ian Campbell wrote:
> On Tue, 2015-01-13 at 14:05 +0000, David Vrabel wrote:
>> Always fully coalesce guest Rx packets into the minimum number of ring
>> slots.  Reducing the number of slots per packet has significant
>> performance benefits (e.g., 7.2 Gbit/s to 11 Gbit/s in an off-host
>> receive test).
>>
>> However, this does increase the number of grant ops per packet which
>> decreases performance with some workloads (intrahost VM to VM)
>> /unless/ grant copy has been optimized for adjacent ops with the same
>> source or destination (see "grant-table: defer releasing pages
>> acquired in a grant copy"[1]).
>>
>> Do we need to retain the existing path and make the always coalesce
>> path conditional on a suitable version of Xen?
>>
>> [1] http://lists.xen.org/archives/html/xen-devel/2015-01/msg01118.html
>>
>> Signed-off-by: David Vrabel <david.vrabel@citrix.com>
> 
> Looks good to me, thanks. Based on that plus the conversation in the
> other subthread:
> 
> Acked-by: Ian Campbell <ian.campbell@citrix.com>

Thanks.  I'll resend with a better commit message.

David