From: Eric Blake <eblake@redhat.com>
To: Anton Nefedov <anton.nefedov@virtuozzo.com>, qemu-devel@nongnu.org
Cc: den@virtuozzo.com, kwolf@redhat.com, mreitz@redhat.com
Subject: Re: [Qemu-devel] [PATCH v2 02/15] file-posix: support BDRV_REQ_ALLOCATE
Date: Thu, 1 Jun 2017 14:49:37 -0500 [thread overview]
Message-ID: <e21f44ea-a5ec-fb51-699a-b6eb06cc11b2@redhat.com> (raw)
In-Reply-To: <1496330073-51338-3-git-send-email-anton.nefedov@virtuozzo.com>
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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 <anton.nefedov@virtuozzo.com>
> ---
> 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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next prev parent reply other threads:[~2017-06-01 19:49 UTC|newest]
Thread overview: 26+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-06-01 15:14 [Qemu-devel] [PATCH v2 00/15] qcow2: space preallocation and COW improvements Anton Nefedov
2017-06-01 15:14 ` [Qemu-devel] [PATCH v2 01/15] block: introduce BDRV_REQ_ALLOCATE flag Anton Nefedov
2017-06-01 19:07 ` Eric Blake
2017-06-02 13:08 ` Anton Nefedov
2017-06-01 15:14 ` [Qemu-devel] [PATCH v2 02/15] file-posix: support BDRV_REQ_ALLOCATE Anton Nefedov
2017-06-01 19:49 ` Eric Blake [this message]
2017-06-01 19:54 ` Eric Blake
2017-06-02 14:34 ` Anton Nefedov
2017-06-01 15:14 ` [Qemu-devel] [PATCH v2 03/15] blkdebug: " Anton Nefedov
2017-06-01 19:50 ` Eric Blake
2017-06-02 13:13 ` Anton Nefedov
2017-06-01 15:14 ` [Qemu-devel] [PATCH v2 04/15] qcow2: alloc space for COW in one chunk Anton Nefedov
2017-06-05 14:28 ` Eric Blake
2017-06-01 15:14 ` [Qemu-devel] [PATCH v2 05/15] qcow2: do not COW the empty areas Anton Nefedov
2017-06-05 14:40 ` Eric Blake
2017-06-01 15:14 ` [Qemu-devel] [PATCH v2 06/15] qcow2: preallocation at image expand Anton Nefedov
2017-06-01 15:14 ` [Qemu-devel] [PATCH v2 07/15] qcow2: set inactive flag Anton Nefedov
2017-06-01 15:14 ` [Qemu-devel] [PATCH v2 08/15] qcow2: truncate preallocated space Anton Nefedov
2017-06-01 15:14 ` [Qemu-devel] [PATCH v2 09/15] qcow2: check space leak at the end of the image Anton Nefedov
2017-06-01 15:14 ` [Qemu-devel] [PATCH v2 10/15] qcow2: handle_prealloc(): find out if area zeroed by earlier preallocation Anton Nefedov
2017-06-01 15:14 ` [Qemu-devel] [PATCH v2 11/15] qcow2: fix misleading comment about L2 linking Anton Nefedov
2017-06-01 15:14 ` [Qemu-devel] [PATCH v2 12/15] qcow2-cluster: slightly refactor handle_dependencies() Anton Nefedov
2017-06-01 15:14 ` [Qemu-devel] [PATCH v2 13/15] qcow2-cluster: make handle_dependencies() logic easier to follow Anton Nefedov
2017-06-01 15:14 ` [Qemu-devel] [PATCH v2 14/15] qcow2: allow concurrent unaligned writes to the same clusters Anton Nefedov
2017-06-01 15:14 ` [Qemu-devel] [PATCH v2 15/15] iotest 046: test simultaneous cluster write error case Anton Nefedov
2017-06-01 18:41 ` [Qemu-devel] [PATCH v2 00/15] qcow2: space preallocation and COW improvements John Snow
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