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Re: [Qemu-devel] Throttling groups vs filter nodes
From: |
Alberto Garcia |
Subject: |
Re: [Qemu-devel] Throttling groups vs filter nodes |
Date: |
Tue, 30 May 2017 15:12:21 +0200 |
User-agent: |
Notmuch/0.18.2 (http://notmuchmail.org) Emacs/24.4.1 (i586-pc-linux-gnu) |
On Mon 29 May 2017 10:57:37 PM CEST, Manos Pitsidianakis wrote:
>>> A quirk in the current implementation is that the throttling limits
>>> for the group are overwritten by each -drive throttling.group=group0.
>>> Limits for all but the last -drive in a group are ignored.
>> - bps or iops != 0 -> set the I/O limits of a throttling group. The
>> selected device is moved to that group if it
>> wasn't there yet.
>>
>> - bps and iops == 0 -> remove a device from a throttling group
>> without touching that group's I/O limits.
>
> These are very unintuitive. However, even without considering
> backwards compatibility, I think that using -object notation (eg
> "object-add throttle-group,id=foo,iops=...) is intuitive in the case
> of groups, but not when you need individual limits for each device as
> the syntax would be too verbose. Of course the old interface covers
> that.
Yes, that's clear. I think that when adding drives, the command-line UI
-drive throttling.iops=XXX notation is good enough for individual
devices and the -object notation is good for groups.
My question was about the block_set_io_throttle QMP command, which you
can use to change the limits of existing drives.
But I think Kevin is right and we should probably think of an
alternative interface for that.
Berto