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Re: [Qemu-devel] [PATCH] block: Add -drive detect_zero=on|off option to
From: |
Eric Blake |
Subject: |
Re: [Qemu-devel] [PATCH] block: Add -drive detect_zero=on|off option to detect all zero writes. |
Date: |
Mon, 30 Jul 2012 08:03:55 -0600 |
User-agent: |
Mozilla/5.0 (X11; Linux x86_64; rv:14.0) Gecko/20120717 Thunderbird/14.0 |
On 07/30/2012 07:57 AM, Paolo Bonzini wrote:
> Il 30/07/2012 15:51, Richard W.M. Jones ha scritto:
>>>> Or just finish up discard support and use the existing fstrim command of
>>>> qemu-ga. :)
>> What's actually involved to do this? I noticed that a virtio-scsi on
>> qcow2 v3 device exported to the guest does not appear to support TRIM
>> at all (see attached test script and output).
>
> The most basic thing to do is to pass -device discard_granularity=NNN,
> where NNN should be the cluster size of the device. On top of this you
> need to add the ability to do TRIM asynchronously, quite some testing,
> and perhaps improving the disk formats so that they support
> sector-granularity discard.
>
> Patches for asynchronous TRIM are in the works (the threadpool patches
> on the list are the first step).
>
> Long term I would like the ability to distinguish
> discard-for-thin-provisioning ("may cause fragmentation, all subsequent
> accesses could be slower") from discard-for-wear-leveling ("only the
> first subsequent access would be slowed down"). This requires changes
> at all levels (host kernel, QEMU, management, guest kernel, and possibly
> guest applications).
Ooh, nice bullet point to add to my upcoming presentation at Linux
Plumber's Conference in a month:
http://summit.linuxplumbersconf.org/lpc-2012/meeting/33/lpc2012-ref-improved-virt-disk-handling/
Does anyone else have some annoyances about large sparse file handling
where improving the kernel would make our life easier, that I should
incorporate into my discussion?
--
Eric Blake address@hidden +1-919-301-3266
Libvirt virtualization library http://libvirt.org
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- [Qemu-devel] [PATCH] Detect zero writes (for discussion only, not to be applied), Richard W.M. Jones, 2012/07/26
- [Qemu-devel] [PATCH] block: Add -drive detect_zero=on|off option to detect all zero writes., Richard W.M. Jones, 2012/07/26
- Re: [Qemu-devel] [PATCH] block: Add -drive detect_zero=on|off option to detect all zero writes., Anthony Liguori, 2012/07/27
- Re: [Qemu-devel] [PATCH] block: Add -drive detect_zero=on|off option to detect all zero writes., Paolo Bonzini, 2012/07/27
- Re: [Qemu-devel] [PATCH] block: Add -drive detect_zero=on|off option to detect all zero writes., Richard W.M. Jones, 2012/07/30
- Re: [Qemu-devel] [PATCH] block: Add -drive detect_zero=on|off option to detect all zero writes., Paolo Bonzini, 2012/07/30
- Re: [Qemu-devel] [PATCH] block: Add -drive detect_zero=on|off option to detect all zero writes.,
Eric Blake <=
- Re: [Qemu-devel] [PATCH] block: Add -drive detect_zero=on|off option to detect all zero writes., Paolo Bonzini, 2012/07/30
- Re: [Qemu-devel] [PATCH] block: Add -drive detect_zero=on|off option to detect all zero writes., Kevin Wolf, 2012/07/30
- Re: [Qemu-devel] [PATCH] block: Add -drive detect_zero=on|off option to detect all zero writes., Richard W.M. Jones, 2012/07/30
Re: [Qemu-devel] [PATCH] Detect zero writes (for discussion only, not to be applied), Anthony Liguori, 2012/07/27