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[Qemu-block] Block Migration and CPU throttling
From: |
Peter Lieven |
Subject: |
[Qemu-block] Block Migration and CPU throttling |
Date: |
Tue, 19 Sep 2017 15:36:38 +0200 |
User-agent: |
Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.2.1 |
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.
Peter
- [Qemu-block] Block Migration and CPU throttling,
Peter Lieven <=
Re: [Qemu-block] Block Migration and CPU throttling, Paolo Bonzini, 2017/09/19