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From: Paolo Bonzini <pbonzini@redhat.com>
To: Peter Lieven <pl@kamp.de>, Fam Zheng <famz@redhat.com>
Cc: "qemu-devel@nongnu.org" <qemu-devel@nongnu.org>,
	qemu block <qemu-block@nongnu.org>
Subject: Re: [Qemu-devel] callout to *file in bdrv_co_get_block_status
Date: Fri, 31 Mar 2017 12:20:10 +0200	[thread overview]
Message-ID: <b5f8ef2d-b014-c5c5-f3a2-cd6aee8116ca@redhat.com> (raw)
In-Reply-To: <3c972a26-18a1-2636-ed80-6b73b972401d@kamp.de>



On 31/03/2017 09:55, Peter Lieven wrote:
>>> Would it be an idea to introduce an inverse flag live BDRV_BLOCK_NOT_ZERO
>>> for cases where we know that there is really DATA and thus can avoid the
>>> second callout?
>> How would you know that a block is nonzero?
> I would trust the metadata. At least for VMDK and QCOW2v3.
> Bad idea?

The metadata only tells you that a block is zero, not that it's nonzero.
 What you are suggesting is really the same as removing the recursion.
However, I still haven't understood clearly if it's a QEMU or tmpfs bug;
if it's a tmpfs bug your suggestion would not fix tmpfs slowness on raw
images.

Paolo

  reply	other threads:[~2017-03-31 10:20 UTC|newest]

Thread overview: 23+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2017-03-17 10:45 [Qemu-devel] callout to *file in bdrv_co_get_block_status Peter Lieven
2017-03-17 10:59 ` Paolo Bonzini
2017-03-17 11:11   ` Peter Lieven
2017-03-17 11:16     ` Paolo Bonzini
2017-03-17 11:20       ` Peter Lieven
2017-03-20  2:46         ` Fam Zheng
2017-03-20 11:21           ` Paolo Bonzini
2017-03-20 11:49             ` Fam Zheng
2017-03-20 12:17               ` Peter Lieven
2017-03-20 12:47               ` Peter Lieven
2017-03-20 13:13                 ` Peter Lieven
2017-03-20 13:23                   ` Paolo Bonzini
2017-03-20 13:35                     ` Peter Lieven
2017-03-20 14:05                       ` Paolo Bonzini
2017-03-20 16:43                         ` Peter Lieven
2017-03-20 16:56                           ` Paolo Bonzini
2017-03-27 13:21                             ` Peter Lieven
2017-03-27 15:06                               ` Paolo Bonzini
2017-03-31  7:55                                 ` Peter Lieven
2017-03-31 10:20                                   ` Paolo Bonzini [this message]
2017-03-17 11:24       ` Fam Zheng
2017-03-17 14:51         ` Paolo Bonzini
2017-03-18 16:16           ` Peter Lieven

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