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Re: [Qemu-devel] [PATCH 2/6] qmp: add query-block-dirty-bitmap-ranges
From: |
Stefan Hajnoczi |
Subject: |
Re: [Qemu-devel] [PATCH 2/6] qmp: add query-block-dirty-bitmap-ranges |
Date: |
Wed, 10 Feb 2016 10:08:25 +0000 |
User-agent: |
Mutt/1.5.24 (2015-08-30) |
On Sat, Jan 30, 2016 at 01:56:30PM +0300, Vladimir Sementsov-Ogievskiy wrote:
> Add qmp command to query dirty bitmap contents. This is needed for
> external backup.
>
> Signed-off-by: Vladimir Sementsov-Ogievskiy <address@hidden>
> ---
> block/dirty-bitmap.c | 55 +++++++++++++++++++++++++++++++++++++++
> blockdev.c | 62
> ++++++++++++++++++++++++++++++++++++++++++++
> include/block/dirty-bitmap.h | 7 +++++
> qapi/block-core.json | 54 ++++++++++++++++++++++++++++++++++++++
> qmp-commands.hx | 33 +++++++++++++++++++++++
> 5 files changed, 211 insertions(+)
This API produces large replies and/or requires many calls to fetch all
bitmap data. The worst case is a 101010... bitmap.
I consider the dirty bitmap to be data (vs control) and not something
that should be sent over a control channel like the QMP monitor.
How about writing the dirty bitmap to a file? The new bitmap file
format that Fam is working on could be used. That way the dirty bitmap
can be saved asynchronously without hogging the QMP monitor.
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