Re: [PATCH v5 0/7] Live Migration With IAA

[Peter Xu <peterx@redhat.com>]

On Thu, Mar 28, 2024 at 03:02:30AM +0000, Liu, Yuan1 wrote:
> Yes, I will support software fallback to ensure CI testing and users can 
> still use qpl compression without IAA hardware.
> 
> Although the qpl software solution will have better performance than zlib, 
> I still don't think it has a greater advantage than zstd. I don't think there
> is a need to add a migration option to configure the qpl software or hardware path.
> So I will still only use QPL as an independent compression in the next version, and
> no other migration options are needed.

That should be fine.

> 
> I will also add a guide to qpl-compression.rst about IAA permission issues and how to
> determine whether the hardware path is available.

OK.

[...]

> > > Yes, I use iperf3 to check the bandwidth for one core, the bandwith is
> > 60Gbps.
> > > [ ID] Interval           Transfer     Bitrate         Retr  Cwnd
> > > [  5]   0.00-1.00   sec  7.00 GBytes  60.1 Gbits/sec    0   2.87 MBytes
> > > [  5]   1.00-2.00   sec  7.05 GBytes  60.6 Gbits/sec    0   2.87 Mbytes
> > >
> > > And in the live migration test, a multifd thread's CPU utilization is
> > almost 100%
> > 
> > This 60Gpbs per-channel is definitely impressive..
> > 
> > Have you tried migration without multifd on your system? Would that also
> > perform similarly v.s. 2 channels multifd?
> 
> Simple Test result below:
> VM Type: 16vCPU, 64G memory
> Workload in VM: fill 56G memory with Silesia data and vCPUs are idle
> Migration Configurations:
> 1. migrate_set_parameter max-bandwidth 100G
> 2. migrate_set_parameter downtime-limit 300
> 3. migrate_set_capability multifd on (multiFD test case)
> 4. migrate_set_parameter multifd-channels 2 (multiFD test case)
> 
>                   Totaltime (ms) Downtime (ms) Throughput (mbps) Pages-per-second
> without Multifd	23580	            307	         21221	       689588
> Multifd 2	       7657	            198	         65410	      2221176

Thanks for the test results.

So I am guessing the migration overheads besides pushing the socket is high
enough to make it drop drastically, even if in this case zero detection
shouldn't play a major role considering most of guest mem is pre-filled.

-- 
Peter Xu