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From: Alberto Garcia <berto@igalia.com>
To: Anton Nefedov <anton.nefedov@virtuozzo.com>, qemu-block@nongnu.org
Cc: kwolf@redhat.com, vsementsov@virtuozzo.com, den@virtuozzo.com,
	qemu-devel@nongnu.org, mreitz@redhat.com,
	Anton Nefedov <anton.nefedov@virtuozzo.com>
Subject: Re: [Qemu-devel] [PATCH v14 1/1] qcow2: skip writing zero buffers to empty COW areas
Date: Wed, 22 May 2019 13:33:41 +0200	[thread overview]
Message-ID: <w51d0kag1uy.fsf@maestria.local.igalia.com> (raw)
In-Reply-To: <20190516142749.81019-2-anton.nefedov@virtuozzo.com>

On Thu 16 May 2019 04:27:49 PM CEST, Anton Nefedov wrote:
> If COW areas of the newly allocated clusters are zeroes on the backing
> image, efficient bdrv_write_zeroes(flags=BDRV_REQ_NO_FALLBACK) can be
> used on the whole cluster instead of writing explicit zero buffers later
> in perform_cow().
>
> iotest 060:
> write to the discarded cluster does not trigger COW anymore.
> Use a backing image instead.
>
> Signed-off-by: Anton Nefedov <anton.nefedov@virtuozzo.com>

Reviewed-by: Alberto Garcia <berto@igalia.com>

Berto


  parent reply	other threads:[~2019-05-22 11:35 UTC|newest]

Thread overview: 9+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-05-16 14:27 [Qemu-devel] [PATCH v14 0/1] qcow2: cluster space preallocation Anton Nefedov
2019-05-16 14:27 ` [Qemu-devel] [PATCH v14 1/1] qcow2: skip writing zero buffers to empty COW areas Anton Nefedov
2019-05-16 14:51   ` Vladimir Sementsov-Ogievskiy
2019-05-22 11:33   ` Alberto Garcia [this message]
2019-05-22 20:40   ` Max Reitz
2019-05-23 12:45     ` Anton Nefedov
2019-05-24 13:56 ` [Qemu-devel] [PATCH v14 0/1] qcow2: cluster space preallocation Max Reitz
2019-05-26 15:01   ` Alberto Garcia
2019-05-27 12:14     ` Max Reitz

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