From: Kevin Wolf <kwolf@redhat.com>
To: Alberto Garcia <berto@igalia.com>
Cc: Anton Nefedov <anton.nefedov@virtuozzo.com>,
Denis Lunev <den@virtuozzo.com>,
"qemu-block@nongnu.org" <qemu-block@nongnu.org>,
"qemu-devel@nongnu.org" <qemu-devel@nongnu.org>,
Max Reitz <mreitz@redhat.com>
Subject: Re: [Qemu-devel] [RFC] Re-evaluating subcluster allocation for qcow2 images
Date: Fri, 28 Jun 2019 11:20:57 +0200 [thread overview]
Message-ID: <20190628092057.GA5179@dhcp-200-226.str.redhat.com> (raw)
In-Reply-To: <w517e97dogw.fsf@maestria.local.igalia.com>
Am 27.06.2019 um 17:42 hat Alberto Garcia geschrieben:
> On Thu 27 Jun 2019 05:38:56 PM CEST, Alberto Garcia wrote:
> >> I would consider 64k cluster/8k subcluster as too extreme for me.
>
> I forgot to add: this 64k/8k ratio is only with my current prototype.
>
> In practice if we go with the 128-bit L2 entries we would have 64
> subclusters per cluster, or 32 if we want to have a separate
> QCOW_OFLAG_ZERO for each subcluster (would we need this?).
Yes, I think we'd want to have a separate zero flag for each subcluster.
Otherwise, when writing to a zero cluster, you'd have to COW the whole
supercluster again. And you'd have to fall back to explicit writes of a
zeroed buffer rather than using efficient operations more often.
Kevin
next prev parent reply other threads:[~2019-06-28 9:22 UTC|newest]
Thread overview: 29+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-06-27 13:59 [Qemu-devel] [RFC] Re-evaluating subcluster allocation for qcow2 images Alberto Garcia
2019-06-27 14:19 ` Denis Lunev
2019-06-27 15:38 ` Alberto Garcia
2019-06-27 15:42 ` Alberto Garcia
2019-06-28 9:20 ` Kevin Wolf [this message]
2019-06-28 9:53 ` Alberto Garcia
2019-06-28 10:04 ` Kevin Wolf
2019-06-28 13:19 ` Alberto Garcia
2019-06-28 14:16 ` Kevin Wolf
2019-06-28 16:31 ` Alberto Garcia
2019-06-27 16:05 ` Denis Lunev
2019-06-28 14:43 ` Alberto Garcia
2019-06-28 14:47 ` Denis Lunev
2019-06-28 14:57 ` Kevin Wolf
2019-06-28 15:02 ` Alberto Garcia
2019-06-28 15:03 ` Denis Lunev
2019-06-28 15:10 ` Alberto Garcia
2019-06-28 15:15 ` Kevin Wolf
2019-06-28 15:09 ` Kevin Wolf
2019-06-28 15:12 ` Alberto Garcia
2019-07-01 6:22 ` Kevin Wolf
2019-06-27 16:54 ` Kevin Wolf
2019-06-27 17:08 ` Denis Lunev
2019-06-28 16:32 ` Alberto Garcia
2019-07-11 14:08 ` Alberto Garcia
2019-07-11 14:32 ` Kevin Wolf
2019-07-11 14:56 ` Alberto Garcia
2019-06-28 12:57 ` Alberto Garcia
2019-06-28 13:03 ` Alberto Garcia
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