Re: [PATCH v4 00/34] migration: File based migration with multifd and fixed-ram

[Fabiano Rosas]

Peter Xu <peterx@redhat.com> writes:

> On Tue, Feb 20, 2024 at 07:41:04PM -0300, Fabiano Rosas wrote:
>> Latest numbers
>> ==============
>> 
>> => guest: 128 GB RAM - 120 GB dirty - 1 vcpu in tight loop dirtying memory
>> => host: 128 CPU AMD EPYC 7543 - 2 NVMe disks in RAID0 (8586 MiB/s) - xfs
>> => pinned vcpus w/ NUMA shortest distances - average of 3 runs - results
>>    from query-migrate
>> 
>> non-live           | time (ms)   pages/s   mb/s   MB/s
>> -------------------+-----------------------------------
>> file               |    110512    256258   9549   1193
>>   + bg-snapshot    |    245660    119581   4303    537
>
> Is this the one using userfault?  I'm surprised it's much slower when
> enabled; logically for a non-live snapshot it should take similar loops
> like a normal migration as it should have zero faults, then it should be
> similar performance.

I just enabled the background-snapshot capability. Is there extra setup
that must be done to enable this properly? The ufd_version_check from
migration-test returns true on this system.

>> -------------------+-----------------------------------
>> fixed-ram          |    157975    216877   6672    834
>>   + multifd 8 ch.  |     95922    292178  10982   1372
>>      + direct-io   |     23268   1936897  45330   5666
>> -------------------------------------------------------
>> 
>> live               | time (ms)   pages/s   mb/s   MB/s
>> -------------------+-----------------------------------
>> file               |         -         -      -      - (file grew 4x the VM 
>> size)
>>   + bg-snapshot    |    357635    141747   2974    371
>> -------------------+-----------------------------------
>> fixed-ram          |         -         -      -      - (no convergence in 5 
>> min)
>>   + multifd 8 ch.  |    230812    497551  14900   1862
>>      + direct-io   |     27475   1788025  46736   5842
>> -------------------------------------------------------
>
> Also surprised on direct-io too.. that is definitely something tremendous.

Indeed. That was the intention with this series all along after all.