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Re: [Qemu-devel] qcow2 performance plan
From: |
Avi Kivity |
Subject: |
Re: [Qemu-devel] qcow2 performance plan |
Date: |
Tue, 14 Sep 2010 19:23:30 +0200 |
User-agent: |
Mozilla/5.0 (X11; U; Linux x86_64; en-US; rv:1.9.2.9) Gecko/20100907 Fedora/3.1.3-1.fc13 Lightning/1.0b3pre Thunderbird/3.1.3 |
On 09/14/2010 07:08 PM, Anthony Liguori wrote:
Yes, I hit this too. So without this patch, it does serialize all
allocating writes?
Yes, but my patch is not enough as it turns out.
When dealing with O_DIRECT, we have to handle RMW on our own which
means we need to serialize access to the same sector.
The way we're planning on addressing this in the short term is to
break the single allocator queue into a per-L2 table queue. So writes
to the same L2 would be serialized but writes to different L2s would
not be serialized.
So at least I read the code correctly.
The next step (also addressed in the qcow2 performance plan) is to batch
writes to L2. You'd actually expect to have many concurrent allocating
writes to one L2. The first is sent to disk, but the following ones
just mark the L2 dirty. When the write returns, it sees it's still
dirty and goes back to disk again.
--
error compiling committee.c: too many arguments to function
- [Qemu-devel] qcow2 performance plan, Avi Kivity, 2010/09/14
- Re: [Qemu-devel] qcow2 performance plan, Anthony Liguori, 2010/09/14
- Re: [Qemu-devel] qcow2 performance plan, Kevin Wolf, 2010/09/14
- Re: [Qemu-devel] qcow2 performance plan, Anthony Liguori, 2010/09/14
- Re: [Qemu-devel] qcow2 performance plan, Kevin Wolf, 2010/09/14
- Re: [Qemu-devel] qcow2 performance plan, Stefan Hajnoczi, 2010/09/14
- Re: [Qemu-devel] qcow2 performance plan, Anthony Liguori, 2010/09/14
- Re: [Qemu-devel] qcow2 performance plan, Avi Kivity, 2010/09/14
- Re: [Qemu-devel] qcow2 performance plan, Anthony Liguori, 2010/09/14
- Re: [Qemu-devel] qcow2 performance plan,
Avi Kivity <=
- Re: [Qemu-devel] qcow2 performance plan, Anthony Liguori, 2010/09/14
[Qemu-devel] Re: qcow2 performance plan, Kevin Wolf, 2010/09/14
Re: [Qemu-devel] qcow2 performance plan, Anthony Liguori, 2010/09/14