From: Paolo Bonzini <pbonzini@redhat.com>
To: "Richard W.M. Jones" <rjones@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: Tue, 07 Jan 2014 15:48:54 +0100 [thread overview]
Message-ID: <52CC13D6.6000607@redhat.com> (raw)
In-Reply-To: <20140102161503.GA14565@redhat.com>
Il 02/01/2014 17:15, Richard W.M. Jones ha scritto:
>
> My (possibly weak) understanding of the upstream qemu code is that
> unmap/discard/trim is not supported in qcow2. It is only supported in
> raw files when using a POSIX-like host OS which has either of:
>
> - block devices supporting BLKDISCARDZEROES
> - files on XFS
> - files on other filesystems that support FALLOC_FL_PUNCH_HOLE (eg ext4)
It doesn't have to support BLKDISCARDZEROES, only BLKDISCARD. I test it
with scsi_debug using both lbprz=0 and lbprz=1 (which becomes
BLKDISCARDZEROES unset and set respectively).
Otherwise this is correct.
> Having said that, I did some tests using libguestfs and I could not
> show that unmap was working, either using raw or qcow2 (both on ext4),
> with virtio-scsi, and recent kernel & qemu. I did not see any errors,
> but also I don't see what I'm doing wrong.
Can you share more?
Paolo
next prev parent reply other threads:[~2014-01-07 14:49 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 [this message]
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
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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