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Re: [Qemu-devel] [PATCH v1 04/13] qcow2: preallocation at image expand
From: |
Eric Blake |
Subject: |
Re: [Qemu-devel] [PATCH v1 04/13] qcow2: preallocation at image expand |
Date: |
Mon, 22 May 2017 14:29:53 -0500 |
User-agent: |
Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.1.0 |
On 05/19/2017 04:34 AM, Anton Nefedov wrote:
> From: "Denis V. Lunev" <address@hidden>
>
> This patch adds image preallocation at expand to provide better locality
> of QCOW2 image file and optimize this procedure for some distributed
> storages where this procedure is slow.
>
> Image expand requests have to be suspended until the allocation is
> performed which is done via special QCowL2Meta.
> This meta is invisible to handle_dependencies() code.
> This is the main reason for also calling preallocation before metadata
> write: it might intersect with preallocation triggered by another IO,
> and has to yield
How does this interact with Max's work on preallocated truncate?
https://lists.gnu.org/archive/html/qemu-devel/2017-04/msg00267.html
--
Eric Blake, Principal Software Engineer
Red Hat, Inc. +1-919-301-3266
Virtualization: qemu.org | libvirt.org
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- [Qemu-devel] [PATCH v1 02/13] qcow2: is_zero_sectors(): return true if area is outside of backing file, (continued)
- [Qemu-devel] [PATCH v1 03/13] qcow2: do not COW the empty areas, Anton Nefedov, 2017/05/19
- [Qemu-devel] [PATCH v1 05/13] qcow2: set inactive flag, Anton Nefedov, 2017/05/19
- [Qemu-devel] [PATCH v1 04/13] qcow2: preallocation at image expand, Anton Nefedov, 2017/05/19
- Re: [Qemu-devel] [PATCH v1 04/13] qcow2: preallocation at image expand,
Eric Blake <=
- [Qemu-devel] [PATCH v1 06/13] qcow2: truncate preallocated space, Anton Nefedov, 2017/05/19
- [Qemu-devel] [PATCH v1 08/13] qcow2: handle_prealloc(): find out if area zeroed by earlier preallocation, Anton Nefedov, 2017/05/19
- [Qemu-devel] [PATCH v1 09/13] qcow2: fix misleading comment about L2 linking, Anton Nefedov, 2017/05/19
- [Qemu-devel] [PATCH v1 07/13] qcow2: check space leak at the end of the image, Anton Nefedov, 2017/05/19
- [Qemu-devel] [PATCH v1 11/13] qcow2-cluster: make handle_dependencies() logic easier to follow, Anton Nefedov, 2017/05/19
- [Qemu-devel] [PATCH v1 13/13] iotest 046: test simultaneous cluster write error case, Anton Nefedov, 2017/05/19
- [Qemu-devel] [PATCH v1 10/13] qcow2-cluster: slightly refactor handle_dependencies(), Anton Nefedov, 2017/05/19
- [Qemu-devel] [PATCH v1 12/13] qcow2: allow concurrent unaligned writes to the same clusters, Anton Nefedov, 2017/05/19