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Re: [Qemu-devel] [PATCH v5 07/12] qemu-img: Empty images after commit
From: |
Kevin Wolf |
Subject: |
Re: [Qemu-devel] [PATCH v5 07/12] qemu-img: Empty images after commit |
Date: |
Wed, 23 Apr 2014 11:32:37 +0200 |
User-agent: |
Mutt/1.5.21 (2010-09-15) |
Am 22.04.2014 um 18:22 hat Max Reitz geschrieben:
> On 22.04.2014 17:19, Eric Blake wrote:
> >On 04/17/2014 03:59 PM, Max Reitz wrote:
> >>After the top image has been committed into an image in its backing
> >>chain, all images above that base image should be emptied to restore the
> >>old qemu-img commit behavior.
> >>
> >>Signed-off-by: Max Reitz <address@hidden>
> >>---
> >> qemu-img.c | 87
> >> +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++---
> >> 1 file changed, 84 insertions(+), 3 deletions(-)
> >Does emptying an image take significant time? If so, does that need to
> >be reflected in the progress meter?
>
> For a 16 GB image I have here (should be nearly full) it took 1:22
> min. Copying it took six minutes, so I guess committing it would
> take even more. I think the ratio is small enough not to include it
> in the progress meter.
Did you check why it took that long? Sounds like we're issuing a lot of
independent discard requests instead of few big ones. Is the image
heavily fragmented?
> Furthermore, I don't see a reasonable implementation for a
> make_empty progress output: As a general implementation for all
> image formats implementing discard will not work (the qcow2
> implementation clearly states that discarded sectors should read
> back as zero)
We can always add new flags or a separate new callback if it improves
things.
Kevin
- Re: [Qemu-devel] [PATCH v5 03/12] blockjob: Introduce block_job_complete_sync(), (continued)
- [Qemu-devel] [PATCH v5 05/12] block/mirror: Improve progress report, Max Reitz, 2014/04/17
- [Qemu-devel] [PATCH v5 06/12] qemu-img: Implement commit like QMP, Max Reitz, 2014/04/17
- [Qemu-devel] [PATCH v5 07/12] qemu-img: Empty images after commit, Max Reitz, 2014/04/17
- Re: [Qemu-devel] [PATCH v5 07/12] qemu-img: Empty images after commit, Eric Blake, 2014/04/22
- Re: [Qemu-devel] [PATCH v5 07/12] qemu-img: Empty images after commit, Max Reitz, 2014/04/22
- Re: [Qemu-devel] [PATCH v5 07/12] qemu-img: Empty images after commit, Max Reitz, 2014/04/22
- Re: [Qemu-devel] [PATCH v5 07/12] qemu-img: Empty images after commit, Eric Blake, 2014/04/22
- Re: [Qemu-devel] [PATCH v5 07/12] qemu-img: Empty images after commit, Max Reitz, 2014/04/22
- Re: [Qemu-devel] [PATCH v5 07/12] qemu-img: Empty images after commit, Eric Blake, 2014/04/22
- Re: [Qemu-devel] [PATCH v5 07/12] qemu-img: Empty images after commit,
Kevin Wolf <=
- Re: [Qemu-devel] [PATCH v5 07/12] qemu-img: Empty images after commit, Max Reitz, 2014/04/24
- Re: [Qemu-devel] [PATCH v5 07/12] qemu-img: Empty images after commit, Kevin Wolf, 2014/04/24
[Qemu-devel] [PATCH v5 08/12] qemu-img: Enable progress output for commit, Max Reitz, 2014/04/17
[Qemu-devel] [PATCH v5 09/12] qemu-img: Specify backing file for commit, Max Reitz, 2014/04/17
[Qemu-devel] [PATCH v5 10/12] iotests: Add _filter_qemu_img_map, Max Reitz, 2014/04/17
[Qemu-devel] [PATCH v5 11/12] iotests: Add test for backing-chain commits, Max Reitz, 2014/04/17