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Re: [Qemu-devel] [PATCH v2 02/15] file-posix: support BDRV_REQ_ALLOCATE
From: |
Eric Blake |
Subject: |
Re: [Qemu-devel] [PATCH v2 02/15] file-posix: support BDRV_REQ_ALLOCATE |
Date: |
Thu, 1 Jun 2017 14:49:37 -0500 |
User-agent: |
Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.1.0 |
On 06/01/2017 10:14 AM, Anton Nefedov wrote:
> Current write_zeroes implementation is good enough to satisfy this flag too
>
> Signed-off-by: Anton Nefedov <address@hidden>
> ---
> block/file-posix.c | 9 ++++++++-
> 1 file changed, 8 insertions(+), 1 deletion(-)
Are we sure that fallocate() is always fast, or are there some file
systems where it is no faster than manually writing zeroes? I'm worried
that blindly claiming BDRV_REQ_ALLOCATE may fail if we encounter a libc
or kernel-based fallback that takes a slow patch on our behalf.
--
Eric Blake, Principal Software Engineer
Red Hat, Inc. +1-919-301-3266
Virtualization: qemu.org | libvirt.org
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- [Qemu-devel] [PATCH v2 00/15] qcow2: space preallocation and COW improvements, Anton Nefedov, 2017/06/01
- [Qemu-devel] [PATCH v2 01/15] block: introduce BDRV_REQ_ALLOCATE flag, Anton Nefedov, 2017/06/01
- [Qemu-devel] [PATCH v2 04/15] qcow2: alloc space for COW in one chunk, Anton Nefedov, 2017/06/01
- [Qemu-devel] [PATCH v2 05/15] qcow2: do not COW the empty areas, Anton Nefedov, 2017/06/01
- [Qemu-devel] [PATCH v2 03/15] blkdebug: support BDRV_REQ_ALLOCATE, Anton Nefedov, 2017/06/01