From: Kevin Wolf <kwolf@redhat.com>
To: Stefan Hajnoczi <stefanha@redhat.com>
Cc: Max Reitz <mreitz@redhat.com>, Eric Blake <eblake@redhat.com>,
qemu-block@nongnu.org, qemu-devel@nongnu.org, berto@igalia.com
Subject: Re: [Qemu-devel] blockdev-add I/O throttling parameters
Date: Mon, 20 Feb 2017 16:45:54 +0100 [thread overview]
Message-ID: <20170220154554.GF4814@noname.redhat.com> (raw)
In-Reply-To: <20170220153012.GK21255@stefanha-x1.localdomain>
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Am 20.02.2017 um 16:30 hat Stefan Hajnoczi geschrieben:
> I/O throttling parameters are missing from blockdev-add. Is this
> intentional?
>
> I can imagine two solutions that do not need these parameters in
> blockdev-add:
>
> 1. I/O throttling is implemented by a BlockDriver. Users are expected
> to create the BDS themselves. This is a little awkward since
> query-block *does* include the throttling parameters in its output
> and we must preserve this behavior for existing users.
>
> 2. block_set_io_throttle must be used after blockdev-add. Suboptimal
> because issuing two commands is not atomic (use transaction?).
>
> Thoughts?
The existing I/O throttling code is working on BlockBackends, but
blockdev-add creates BlockDriverStates. So it can't possibly add
throttling parameters.
The currently recommended solution block_set_io_throttle. The other
option to control BB level thorttling would be to add qdev properties to
the block devices.
In the long term, I think going with 1. and moving throttling to the
block node level is the much nicer (and more flexible) option.
Kevin
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next prev parent reply other threads:[~2017-02-20 15:46 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-02-20 15:30 [Qemu-devel] blockdev-add I/O throttling parameters Stefan Hajnoczi
2017-02-20 15:45 ` Kevin Wolf [this message]
2017-02-20 16:29 ` Alberto Garcia
2017-02-21 11:17 ` [Qemu-devel] [Qemu-block] " Stefan Hajnoczi
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