From: Paolo Bonzini <pbonzini@redhat.com>
To: Kevin Wolf <kwolf@redhat.com>
Cc: Juan Quintela <quintela@redhat.com>,
Stefan Hajnoczi <stefanha@gmail.com>,
qemu-devel <qemu-devel@nongnu.org>,
Dietmar Maurer <dietmar@proxmox.com>,
Wenchao Xia <xiawenc@linux.vnet.ibm.com>
Subject: Re: [Qemu-devel] [RFC] qmp interface for save vmstate to image
Date: Mon, 18 Mar 2013 11:08:56 +0100 [thread overview]
Message-ID: <5146E7B8.9000204@redhat.com> (raw)
In-Reply-To: <20130318090430.GB2476@dhcp-200-207.str.redhat.com>
Il 18/03/2013 10:04, Kevin Wolf ha scritto:
> Oh, seems I misread this then. I thought this was about internal live
> snapshots, which is a feature that I consider really useful. I'm not so
> sure if saving the VM state as the disk contents of a qcow2 image is
> really helpful.
>
> If zero clusters help a lot, then there's clearly something to improve
> in the migration protocol, because it shouldn't send so many zeros in
> the first place.
Zero pages are sent as a single 9-byte entry (64 bits for the address
and flags, 8 for the zero).
I don't expect the migration stream to have a single zero cluster, since
every page is prefixed by the 64 bits for the address and flags.
Furthermore, the RAM data would be horribly unaligned because of this.
15-20% sectors or so would be read twice, since reading each page (4104
bytes including the address and flags) would span 10 sectors (5120 bytes).
Paolo
next prev parent reply other threads:[~2013-03-18 10:09 UTC|newest]
Thread overview: 19+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-03-15 7:24 [Qemu-devel] [RFC] qmp interface for save vmstate to image Wenchao Xia
2013-03-15 14:51 ` Stefan Hajnoczi
2013-03-18 6:40 ` Wenchao Xia
2013-03-18 9:04 ` Kevin Wolf
2013-03-18 10:08 ` Paolo Bonzini [this message]
2013-03-18 10:50 ` Wenchao Xia
2013-03-18 10:47 ` Wenchao Xia
2013-03-18 10:09 ` Stefan Hajnoczi
2013-03-18 13:28 ` Pavel Hrdina
2013-03-21 6:43 ` Wenchao Xia
2013-03-21 11:48 ` Pavel Hrdina
2013-03-21 13:38 ` Stefan Hajnoczi
2013-03-21 13:42 ` Paolo Bonzini
2013-03-21 13:53 ` Pavel Hrdina
2013-03-21 14:56 ` Stefan Hajnoczi
2013-03-21 15:08 ` Eric Blake
2013-03-23 4:36 ` Wenchao Xia
2013-03-27 3:35 ` Wenchao Xia
2013-03-21 13:43 ` Pavel Hrdina
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