From: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
To: Stefan Hajnoczi <stefanha@redhat.com>
Cc: kwolf@redhat.com, Stefan Hajnoczi <stefanha@gmail.com>,
qemu-devel@nongnu.org,
Vladimir Sementsov-Ogievskiy <vsementsov@parallels.com>,
pbonzini@redhat.com, den@openvz.org, jsnow@redhat.com
Subject: Re: [Qemu-devel] [PATCH 1/8] spec: add qcow2-dirty-bitmaps specification
Date: Thu, 11 Jun 2015 13:19:24 +0300 [thread overview]
Message-ID: <557960AC.4080607@virtuozzo.com> (raw)
In-Reply-To: <20150610132420.GD2430@stefanha-thinkpad.home>
On 10.06.2015 16:24, Stefan Hajnoczi wrote:
> On Wed, Jun 10, 2015 at 11:19:30AM +0300, Vladimir Sementsov-Ogievskiy wrote:
>> On 09.06.2015 20:03, Stefan Hajnoczi wrote:
>>> On Mon, Jun 08, 2015 at 06:21:19PM +0300, Vladimir Sementsov-Ogievskiy wrote:
>>>> @@ -166,6 +167,19 @@ the header extension data. Each entry look like this:
>>>> terminated if it has full length)
>>>> +== Dirty bitmaps ==
>>>> +
>>>> +Dirty bitmaps is an optional header extension. It provides a possibility of
>>>> +storing dirty bitmaps in qcow2 image. The fields are:
>>>> +
>>>> + 0 - 3: nb_dirty_bitmaps
>>>> + Number of dirty bitmaps contained in the image
>>> Is there a maximum?
>> hmm. any proposals for this?
> 65535 seems practical.
So, you suggest to reduce this field width to 2b? And additional 2 bytes
reserved field, to achieve 8b-alignment?
>
>>>> +=== Cluster mapping ===
>>>> +
>>>> +Dirty bitmaps are stored using a ONE-level structure for the mapping of
>>>> +bitmaps to host clusters. There is only an L1 table.
>>>> +
>>>> +The L1 table has a variable size (stored in the Bitmap table entry) and may
>>>> +use multiple clusters, however it must be contiguous in the image file.
>>> The use of "L1 table" could be confusing. The refcount metadata uses
>>> "refcount table" and "refcount block" to describe a one-level table.
>> I agree. Hmm.. dirty bitmaps table? ok?
> Yes, that is good.
>
>>>> +
>>>> +Given an offset into the bitmap, the offset into the image file can be
>>>> +obtained as follows:
>>>> +
>>>> + offset = l1_table[offset / cluster_size] + (offset % cluster_size)
>>> It might help to add granularity to this formula.
>>>
>>> Instead of "offset", "bit_number" or "bitnr" might be clearer since
>>> "offset" means something different in other parts of the document.
>> Hmm. In my opinion, the bitmap here is stored as raw data. And granularity
>> is an additional parameter (for deserializing this data). So, it is an
>> offset in bytes for this data. The format is not for accessing bitmap bits,
>> it's only for loading the whole bitmap one time.
> You are right, it wasn't clear when I read this the first time. My
> problem was the "offset into the bitmap" doesn't have any units. So
> let's make this more explicit. Can you document how to go from a bit
> number down to the offset?
--
Best regards,
Vladimir
* now, @virtuozzo.com instead of @parallels.com. Sorry for this inconvenience.
next prev parent reply other threads:[~2015-06-11 10:19 UTC|newest]
Thread overview: 78+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-06-08 15:21 [Qemu-devel] [PATCH v2 RFC 0/8] block: persistent dirty bitmaps Vladimir Sementsov-Ogievskiy
2015-06-08 15:21 ` [Qemu-devel] [PATCH 1/8] spec: add qcow2-dirty-bitmaps specification Vladimir Sementsov-Ogievskiy
2015-06-09 16:01 ` John Snow
2015-06-09 17:03 ` Stefan Hajnoczi
2015-06-10 8:19 ` Vladimir Sementsov-Ogievskiy
2015-06-10 8:49 ` Vladimir Sementsov-Ogievskiy
2015-06-10 13:00 ` Eric Blake
2015-06-11 10:16 ` Vladimir Sementsov-Ogievskiy
2015-06-10 13:24 ` Stefan Hajnoczi
2015-06-11 10:19 ` Vladimir Sementsov-Ogievskiy [this message]
2015-06-11 13:03 ` Stefan Hajnoczi
2015-06-11 16:21 ` John Snow
2015-06-12 10:28 ` Stefan Hajnoczi
2015-06-12 15:19 ` John Snow
2015-06-10 15:34 ` Kevin Wolf
2015-06-11 10:25 ` Vladimir Sementsov-Ogievskiy
2015-06-11 16:30 ` John Snow
2015-06-12 8:33 ` Kevin Wolf
2015-08-24 10:46 ` Vladimir Sementsov-Ogievskiy
2015-08-24 13:30 ` Vladimir Sementsov-Ogievskiy
2015-08-24 14:08 ` Vladimir Sementsov-Ogievskiy
2015-08-24 14:04 ` Vladimir Sementsov-Ogievskiy
2015-08-31 22:21 ` Eric Blake
2015-08-31 22:24 ` John Snow
2015-06-08 15:21 ` [Qemu-devel] [PATCH 2/8] qcow2: add dirty-bitmaps feature Vladimir Sementsov-Ogievskiy
2015-06-09 16:52 ` Stefan Hajnoczi
2015-06-10 14:30 ` Stefan Hajnoczi
2015-06-12 19:02 ` John Snow
2015-06-15 14:42 ` Stefan Hajnoczi
2015-06-23 17:57 ` John Snow
2015-06-24 9:39 ` Stefan Hajnoczi
2015-08-14 17:14 ` Vladimir Sementsov-Ogievskiy
2015-08-26 9:09 ` Stefan Hajnoczi
2015-06-11 23:04 ` John Snow
2015-06-15 14:05 ` Vladimir Sementsov-Ogievskiy
2015-06-15 16:53 ` John Snow
2015-06-12 21:55 ` John Snow
2015-08-26 13:15 ` Vladimir Sementsov-Ogievskiy
2015-08-26 14:14 ` Vladimir Sementsov-Ogievskiy
2015-08-27 12:43 ` Vladimir Sementsov-Ogievskiy
2015-06-08 15:21 ` [Qemu-devel] [PATCH 3/8] block: store persistent dirty bitmaps Vladimir Sementsov-Ogievskiy
2015-06-08 15:21 ` [Qemu-devel] [PATCH 4/8] block: add bdrv_load_dirty_bitmap Vladimir Sementsov-Ogievskiy
2015-06-09 16:01 ` Stefan Hajnoczi
2015-06-10 22:33 ` John Snow
2015-06-11 10:41 ` Vladimir Sementsov-Ogievskiy
2015-06-08 15:21 ` [Qemu-devel] [PATCH 5/8] qcow2: add qcow2_dirty_bitmap_delete_all Vladimir Sementsov-Ogievskiy
2015-06-08 15:21 ` [Qemu-devel] [PATCH 6/8] qcow2: add autoclear bit for dirty bitmaps Vladimir Sementsov-Ogievskiy
2015-06-09 15:49 ` Stefan Hajnoczi
2015-06-09 15:50 ` Stefan Hajnoczi
2015-08-27 7:45 ` Vladimir Sementsov-Ogievskiy
2015-08-31 11:06 ` Vladimir Sementsov-Ogievskiy
2015-08-31 22:39 ` Eric Blake
2015-08-31 22:50 ` Eric Blake
2015-06-10 23:42 ` John Snow
2015-06-11 8:35 ` Kevin Wolf
2015-06-11 10:49 ` Vladimir Sementsov-Ogievskiy
2015-06-11 16:36 ` John Snow
2015-06-08 15:21 ` [Qemu-devel] [PATCH 7/8] qemu: command line option " Vladimir Sementsov-Ogievskiy
2015-06-11 20:57 ` John Snow
2015-06-12 21:49 ` John Snow
2015-06-08 15:21 ` [Qemu-devel] [PATCH 8/8] iotests: test internal persistent dirty bitmap Vladimir Sementsov-Ogievskiy
2015-06-09 16:17 ` Eric Blake
2015-06-10 15:27 ` [Qemu-devel] [PATCH v2 RFC 0/8] block: persistent dirty bitmaps Stefan Hajnoczi
2015-06-11 11:22 ` Vladimir Sementsov-Ogievskiy
2015-06-11 13:14 ` Stefan Hajnoczi
2015-06-11 20:06 ` Stefan Hajnoczi
2015-06-12 9:58 ` Denis V. Lunev
2015-06-12 10:36 ` Stefan Hajnoczi
2015-08-26 6:26 ` Vladimir Sementsov-Ogievskiy
2015-08-26 9:13 ` Stefan Hajnoczi
2015-06-12 19:34 ` John Snow
2015-06-17 14:29 ` Vladimir Sementsov-Ogievskiy
2015-06-24 0:21 ` John Snow
2015-07-08 12:24 ` Vladimir Sementsov-Ogievskiy
2015-07-08 15:21 ` John Snow
2015-08-27 10:08 ` Vladimir Sementsov-Ogievskiy
-- strict thread matches above, loose matches on Subject: below --
2015-01-13 17:02 [Qemu-devel] [PATCH 0/8] block: persistent dirty bitmaps (RFC) Vladimir Sementsov-Ogievskiy
2015-01-13 17:02 ` [Qemu-devel] [PATCH 1/8] spec: add qcow2-dirty-bitmaps specification Vladimir Sementsov-Ogievskiy
2015-01-27 15:39 ` Eric Blake
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