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Re: [Qemu-block] [PATCH v2 08/13] block: Support meta dirty bitmap

From: Vladimir Sementsov-Ogievskiy
Subject: Re: [Qemu-block] [PATCH v2 08/13] block: Support meta dirty bitmap
Date: Tue, 26 Jan 2016 10:49:52 +0300
User-agent: Mozilla/5.0 (X11; Linux x86_64; rv:31.0) Gecko/20100101 Thunderbird/31.8.0

On 26.01.2016 09:25, Fam Zheng wrote:
On Fri, 01/22 15:05, Vladimir Sementsov-Ogievskiy wrote:
In my migration series I need iterators, get granularity, and
something like hbitmap_count  for meta bitmaps. You can add them
here if you want, or I can add them in my series.
Okay, I can add that.

I have one more question on the interface: what dirty bitmaps are going to be
migrated? At this moment there are dirty bitmaps created by block jobs
(drive-mirror), and in-memory dirty bitmaps created for incremental backup;
later there will be persistent dirty bitmaps owned by block drivers (extended
version of qcow2, and in QBM driver I'm working on). Which of them are subject
of migration in your series?

I'm asking because I want to know whether we need to implement multiple meta
bitmaps on one block dirty bitmap.

Only named bitmaps are migrated. For now, only qmp-created bitmaps are named. So, it can be in-memory dirty bitmaps or, in future, persistent dirty bitmaps.

Why multiple meta bitmaps? What is your plan about meta, should it be used for something other than migration? There was ideas about async loading persistent metabitmaps - maybe here? We can disallow processes using meta bitmaps to be simultaneous.

Best regards,
* now, @virtuozzo.com instead of @parallels.com. Sorry for this inconvenience.

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