From: Christoph Hellwig <hch@lst.de>
To: Anthony Liguori <anthony@codemonkey.ws>
Cc: Kevin Wolf <kwolf@redhat.com>,
Stefan Hajnoczi <stefanha@gmail.com>,
qemu-devel@nongnu.org, Avi Kivity <avi@redhat.com>,
Stefan Hajnoczi <stefanha@linux.vnet.ibm.com>
Subject: Re: [Qemu-devel] [RFC] qed: Add QEMU Enhanced Disk format
Date: Fri, 10 Sep 2010 15:52:03 +0200 [thread overview]
Message-ID: <20100910135202.GC28831@lst.de> (raw)
In-Reply-To: <4C8A3509.6060101@codemonkey.ws>
On Fri, Sep 10, 2010 at 08:39:21AM -0500, Anthony Liguori wrote:
> You're hand waving to a dangerous degree here :-)
>
> TRIM in qcow2 would require the following sequence:
>
> 1) remove cluster from L2 table
> 2) sync()
> 3) reduce cluster reference count
> 4) sync()
>
> TRIM needs to be fast so this is not going to be acceptable. How do you
> solve it?
It's utterly slow in any real life SSD.
> For QED, TRIM requires:
>
> 1) remove cluster from L2 table
> 2) sync()
>
> In both cases, I'm assuming we lazily write the free list and have a way
> to detect unclean mounts. Unclean mounts require an fsck() and both
> qcow2 and qed require it.
If you do proper transactional metadata updates you can completely drop
the sync. TRIM / SCSI unmap are optimizations that can just be noops
without compromising data integrity.
next prev parent reply other threads:[~2010-09-10 13:52 UTC|newest]
Thread overview: 132+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-09-06 10:04 [Qemu-devel] [RFC] qed: Add QEMU Enhanced Disk format Stefan Hajnoczi
2010-09-06 10:25 ` Alexander Graf
2010-09-06 10:31 ` Stefan Hajnoczi
2010-09-06 14:21 ` Luca Tettamanti
2010-09-06 14:24 ` Alexander Graf
2010-09-06 16:27 ` Anthony Liguori
2010-09-06 10:27 ` [Qemu-devel] " Kevin Wolf
2010-09-06 12:40 ` Stefan Hajnoczi
2010-09-06 12:57 ` Anthony Liguori
2010-09-06 13:02 ` Stefan Hajnoczi
2010-09-06 14:10 ` Kevin Wolf
2010-09-06 16:45 ` Anthony Liguori
2010-09-06 12:45 ` Anthony Liguori
2010-09-10 23:49 ` H. Peter Anvin
2010-09-06 11:18 ` [Qemu-devel] " Daniel P. Berrange
2010-09-06 12:52 ` Anthony Liguori
2010-09-06 13:35 ` Daniel P. Berrange
2010-09-06 16:38 ` Anthony Liguori
2010-09-06 13:06 ` Anthony Liguori
2010-09-07 14:51 ` Avi Kivity
2010-09-07 15:40 ` Anthony Liguori
2010-09-07 16:09 ` Avi Kivity
2010-09-07 16:25 ` Anthony Liguori
2010-09-07 22:27 ` Anthony Liguori
2010-09-08 8:23 ` Avi Kivity
2010-09-08 8:41 ` Alexander Graf
2010-09-08 8:53 ` Avi Kivity
2010-09-08 11:15 ` Stefan Hajnoczi
2010-09-08 15:38 ` Christoph Hellwig
2010-09-08 16:30 ` Anthony Liguori
2010-09-08 20:23 ` Christoph Hellwig
2010-09-08 20:28 ` Anthony Liguori
2010-09-09 2:35 ` Christoph Hellwig
2010-09-09 6:24 ` Avi Kivity
2010-09-09 21:01 ` Christoph Hellwig
2010-09-10 11:15 ` Avi Kivity
2010-09-09 6:53 ` Avi Kivity
2010-09-10 21:22 ` Jamie Lokier
2010-09-14 10:46 ` Stefan Hajnoczi
2010-09-14 11:08 ` Stefan Hajnoczi
2010-09-14 12:54 ` Anthony Liguori
2010-09-08 12:55 ` Anthony Liguori
2010-09-09 6:30 ` Avi Kivity
2010-09-08 12:48 ` Anthony Liguori
2010-09-08 13:20 ` Kevin Wolf
2010-09-08 13:26 ` Anthony Liguori
2010-09-08 13:46 ` Kevin Wolf
2010-09-09 6:45 ` Avi Kivity
2010-09-09 6:48 ` Avi Kivity
2010-09-09 12:49 ` Anthony Liguori
2010-09-09 16:48 ` [Qemu-devel] " Paolo Bonzini
2010-09-09 17:02 ` Anthony Liguori
2010-09-09 20:56 ` Christoph Hellwig
2010-09-10 10:53 ` Avi Kivity
2010-09-10 11:14 ` [Qemu-devel] " Avi Kivity
2010-09-10 11:25 ` Avi Kivity
2010-09-10 11:33 ` Stefan Hajnoczi
2010-09-10 11:43 ` Avi Kivity
2010-09-10 13:22 ` Anthony Liguori
2010-09-10 13:48 ` Christoph Hellwig
2010-09-10 15:02 ` Anthony Liguori
2010-09-10 15:18 ` Kevin Wolf
2010-09-10 15:53 ` Anthony Liguori
2010-09-10 16:05 ` Kevin Wolf
2010-09-10 17:10 ` Anthony Liguori
2010-09-10 17:44 ` Kevin Wolf
2010-09-10 17:46 ` Miguel Di Ciurcio Filho
2010-09-10 14:02 ` Avi Kivity
2010-09-10 13:47 ` Christoph Hellwig
2010-09-10 14:05 ` Avi Kivity
2010-09-10 14:12 ` Christoph Hellwig
2010-09-10 14:24 ` Avi Kivity
2010-09-10 13:16 ` Anthony Liguori
2010-09-10 14:06 ` Avi Kivity
2010-09-10 11:43 ` Stefan Hajnoczi
2010-09-10 12:06 ` Avi Kivity
2010-09-10 13:28 ` Anthony Liguori
2010-09-10 12:12 ` Kevin Wolf
2010-09-10 12:35 ` Stefan Hajnoczi
2010-09-10 12:47 ` Avi Kivity
2010-09-10 13:10 ` Stefan Hajnoczi
2010-09-10 13:19 ` Avi Kivity
2010-09-10 13:39 ` Anthony Liguori
2010-09-10 13:52 ` Christoph Hellwig [this message]
2010-09-10 13:56 ` Avi Kivity
2010-09-10 13:48 ` Kevin Wolf
2010-09-10 13:14 ` Anthony Liguori
2010-09-10 13:47 ` Avi Kivity
2010-09-10 14:56 ` Anthony Liguori
2010-09-10 15:49 ` Avi Kivity
2010-09-10 17:07 ` Anthony Liguori
2010-09-10 17:42 ` Kevin Wolf
2010-09-10 19:33 ` Anthony Liguori
2010-09-13 10:41 ` Kevin Wolf
2010-09-12 13:24 ` Avi Kivity
2010-09-12 15:13 ` Anthony Liguori
2010-09-12 15:56 ` Avi Kivity
2010-09-12 17:09 ` Anthony Liguori
2010-09-12 17:51 ` Avi Kivity
2010-09-12 20:18 ` Anthony Liguori
2010-09-13 9:24 ` Avi Kivity
2010-09-13 11:28 ` Kevin Wolf
2010-09-13 11:34 ` Avi Kivity
2010-09-13 11:48 ` Kevin Wolf
2010-09-13 13:19 ` Anthony Liguori
2010-09-13 13:12 ` Anthony Liguori
2010-09-13 11:03 ` Kevin Wolf
2010-09-13 13:07 ` Anthony Liguori
2010-09-13 13:24 ` Kevin Wolf
2010-09-07 16:12 ` Anthony Liguori
2010-09-07 21:35 ` Christoph Hellwig
2010-09-07 22:29 ` Anthony Liguori
2010-09-07 22:40 ` Christoph Hellwig
2010-09-08 15:07 ` Stefan Hajnoczi
2010-09-09 6:59 ` Avi Kivity
2010-09-09 17:43 ` Anthony Liguori
2010-09-09 20:46 ` Christoph Hellwig
2010-09-10 11:22 ` Avi Kivity
2010-09-10 11:29 ` Stefan Hajnoczi
2010-09-10 11:37 ` Avi Kivity
2010-09-07 13:58 ` Avi Kivity
2010-09-07 19:25 ` Blue Swirl
2010-09-07 20:41 ` Anthony Liguori
2010-09-08 7:48 ` Kevin Wolf
2010-09-08 15:37 ` Stefan Hajnoczi
2010-09-08 18:24 ` Blue Swirl
2010-09-08 18:35 ` Anthony Liguori
2010-09-08 18:56 ` Blue Swirl
2010-09-08 19:19 ` Anthony Liguori
2010-09-15 21:01 ` [Qemu-devel] " Michael S. Tsirkin
2010-09-15 21:12 ` Anthony Liguori
-- strict thread matches above, loose matches on Subject: below --
2010-09-17 3:51 [Qemu-devel] " Khoa Huynh
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