[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]
Re: [Qemu-block] Block Migration and CPU throttling
From: |
Peter Lieven |
Subject: |
Re: [Qemu-block] Block Migration and CPU throttling |
Date: |
Wed, 20 Sep 2017 21:16:47 +0200 |
User-agent: |
Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.2.1 |
Am 19.09.2017 um 16:41 schrieb Paolo Bonzini:
> On 19/09/2017 15:36, Peter Lieven wrote:
>> Hi,
>>
>> I just noticed that CPU throttling and Block Migration don't work
>> together very well.
>> During block migration the throttling heuristic detects that we
>> obviously make no progress
>> in ram transfer. But the reason is the running block migration and not a
>> too high dirty pages rate.
>>
>> The result is that any VM is throttled by 99% during block migration.
>>
>> I wonder what the best way would be fix this. I came up with the
>> following ideas so far:
>>
>> - disable throttling while block migration is in bulk stage
>> - check if absolute number of num_dirty_pages_period crosses a threshold
>> and not if its just
>> greater than 50% of transferred bytes
>> - check if migration_dirty_pages > 0. This slows down throttling, but
>> does not avoid it completely.
> If you can use nbd-server and drive-mirror for block migration (libvirt
> would do it), then you will use multiple sockets and be able to migrate
> block and RAM at the same time.
>
> Otherwise, disabling throttling during the bulk stage is the one that
> seems nicest and most promising.
Okay, but this can be done independently of the nbd approach.
If someone uses classic block migration and auto converge his
vserver will freeze.
I will send a patch to fix that.
Thanks,
Peter
Re: [Qemu-block] Block Migration and CPU throttling, Paolo Bonzini, 2017/09/19
- Re: [Qemu-block] Block Migration and CPU throttling,
Peter Lieven <=