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Re: [Qemu-devel] TRIM/DISCARD/UNMAP support on qemu-nbd
From: |
Paolo Bonzini |
Subject: |
Re: [Qemu-devel] TRIM/DISCARD/UNMAP support on qemu-nbd |
Date: |
Tue, 07 Jan 2014 15:48:54 +0100 |
User-agent: |
Mozilla/5.0 (X11; Linux x86_64; rv:17.0) Gecko/20130923 Thunderbird/17.0.9 |
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
- Re: [Qemu-devel] TRIM/DISCARD/UNMAP support on qemu-nbd, Richard W.M. Jones, 2014/01/02
- Re: [Qemu-devel] TRIM/DISCARD/UNMAP support on qemu-nbd,
Paolo Bonzini <=
- Re: [Qemu-devel] TRIM/DISCARD/UNMAP support on qemu-nbd, Richard W.M. Jones, 2014/01/07
- Re: [Qemu-devel] TRIM/DISCARD/UNMAP support on qemu-nbd, Paolo Bonzini, 2014/01/07
- Re: [Qemu-devel] TRIM/DISCARD/UNMAP support on qemu-nbd, Richard W.M. Jones, 2014/01/07
- Re: [Qemu-devel] TRIM/DISCARD/UNMAP support on qemu-nbd, Richard W.M. Jones, 2014/01/07
- Re: [Qemu-devel] TRIM/DISCARD/UNMAP support on qemu-nbd, Paolo Bonzini, 2014/01/08
- Re: [Qemu-devel] TRIM/DISCARD/UNMAP support on qemu-nbd, Richard W.M. Jones, 2014/01/08
- Re: [Qemu-devel] TRIM/DISCARD/UNMAP support on qemu-nbd, Paolo Bonzini, 2014/01/08
- Re: [Qemu-devel] TRIM/DISCARD/UNMAP support on qemu-nbd, Richard W.M. Jones, 2014/01/08
- Re: [Qemu-devel] TRIM/DISCARD/UNMAP support on qemu-nbd, Paolo Bonzini, 2014/01/09