Re: [Qemu-devel] [PATCH v5 10/12] rdma: introduce capability x-rdma-pin-all

["Michael R. Hines" <mrhines@linux.vnet.ibm.com>]

On 04/22/2013 04:24 PM, Eric Blake wrote:
> On 04/21/2013 03:17 PM, mrhines@linux.vnet.ibm.com wrote:
>> From: "Michael R. Hines" <mrhines@us.ibm.com>
>>
>> This capability allows you to disable dynamic chunk registration
>> for better throughput on high-performance links.
>>
>> For example, using an 8GB RAM virtual machine with all 8GB of memory in
>> active use and the VM itself is completely idle using a 40 gbps infiniband link:
>>
>> 1. x-pin-all disabled total time: approximately 7.5 seconds @ 9.5 Gbps
>> 2. x-pin-all enabled total time: approximately 4 seconds @ 26 Gbps
> Naming here doesn't match the actual bit name; but it is obvious enough
> to know what you meant.
>
> Thanks for doing this, by the way - the default-to-disabled is a bit
> nicer to manage from libvirt's perspective.
>
>> These numbers would of course scale up to whatever size virtual machine
>> you have to migrate using RDMA.
>>
>> Enabling this feature does *not* have any measurable affect on
>> migration *downtime*. This is because, without this feature, all of the
>> memory will have already been registered already in advance during
>> the bulk round and does not need to be re-registered during the successive
>> iteration rounds.
>>
>> Signed-off-by: Michael R. Hines <mrhines@us.ibm.com>
>> ---
>>   include/migration/migration.h |    2 ++
>>   migration.c                   |    9 +++++++++
>>   qapi-schema.json              |    7 ++++++-
>>   3 files changed, 17 insertions(+), 1 deletion(-)
>
>> +++ b/qapi-schema.json
>> @@ -602,10 +602,15 @@
>>   #          This feature allows us to minimize migration traffic for certain work
>>   #          loads, by sending compressed difference of the pages
>>   #
>> +# @x-rdma-pin-all: (since 1.5) Controls whether or not the entire VM memory footprint is
> Trailing whitespace, and line longer than 80 columns.  You ought to
> rewrap this, and make sure it passes checkpatch.pl.
>
> But since that is whitespace-only, feel free to add:
>
> Reviewed-by: Eric Blake <eblake@redhat.com>
>

Acknowledged.