From: "Richard W.M. Jones" <rjones@redhat.com>
To: Paolo Bonzini <pbonzini@redhat.com>
Cc: Teng-Feng Yang <shinrairis@gmail.com>, qemu-devel@nongnu.org
Subject: Re: [Qemu-devel] TRIM/DISCARD/UNMAP support on qemu-nbd
Date: Wed, 8 Jan 2014 22:24:35 +0000 [thread overview]
Message-ID: <20140108222435.GO4802@redhat.com> (raw)
In-Reply-To: <52CDCD17.8070508@redhat.com>
On Wed, Jan 08, 2014 at 11:11:35PM +0100, Paolo Bonzini wrote:
> Is guestfish using "discard=on"?
No.
Adding the discard=on parameter does indeed fix this:
13M /tmp/test1
17M /tmp/test2
However why isn't this the default? Is there a case where discard=on
would be undesirable?
It's extremely difficult to know when it's safe to add this parameter.
Qemu gives no indication of when using discard=.. is safe (ie. won't
cause qemu to fail to start up or fail in some other way). It's even
worse when we have to go via libvirt which itself doesn't expose
qemu's capabilities upwards.
Rich.
--
Richard Jones, Virtualization Group, Red Hat http://people.redhat.com/~rjones
Fedora Windows cross-compiler. Compile Windows programs, test, and
build Windows installers. Over 100 libraries supported.
http://fedoraproject.org/wiki/MinGW
next prev parent reply other threads:[~2014-01-08 22:24 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-12-30 11:58 [Qemu-devel] TRIM/DISCARD/UNMAP support on qemu-nbd Teng-Feng Yang
2014-01-02 16:15 ` Richard W.M. Jones
2014-01-07 14:48 ` Paolo Bonzini
2014-01-07 20:27 ` Richard W.M. Jones
2014-01-07 20:48 ` Paolo Bonzini
2014-01-07 21:22 ` Richard W.M. Jones
2014-01-08 22:11 ` Paolo Bonzini
2014-01-08 22:24 ` Richard W.M. Jones [this message]
2014-01-08 22:45 ` Paolo Bonzini
2014-01-08 22:53 ` Richard W.M. Jones
2014-01-09 7:02 ` Paolo Bonzini
2014-01-07 21:27 ` Richard W.M. Jones
2014-01-06 2:45 ` Stefan Hajnoczi
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