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Re: [Qemu-devel] [RFC] Disk integrity in QEMU
From: |
Paul Brook |
Subject: |
Re: [Qemu-devel] [RFC] Disk integrity in QEMU |
Date: |
Fri, 10 Oct 2008 15:05:41 +0100 |
User-agent: |
KMail/1.9.9 |
On Friday 10 October 2008, Anthony Liguori wrote:
> Paul Brook wrote:
> >> But that said, I'm concerned that this is far too confusing for users.
> >> I don't think anyone is relying on disk write performance when in
> >> write-back mode simply because the guest already has a page cache so
> >> writes are already being completed instantaneously from the
> >> application's perspective.
> >
> > This isn't entirely true. With IDE devices you don't have command
> > queueing, so it's easy for a large write to stall subsequent reads for a
> > relatively long time.
> > I'm not sure how much this effects qemu, but I've definitely seen it
> > happening on real hardware.
>
> I think that suggests we should have a cache=wb option and if people
> report slow downs with IDE, we can observe if cache=wb helps. My
> suspicion is that it's not going to have a practical impact because as
> long as the operations are asynchronous (via DMA), then you're getting
> native-like performance.
Sounds reasonable to me.
Paul
- Re: [Qemu-devel] [RFC] Disk integrity in QEMU, (continued)
- Re: [Qemu-devel] [RFC] Disk integrity in QEMU, Aurelien Jarno, 2008/10/10
- Re: [Qemu-devel] [RFC] Disk integrity in QEMU, Anthony Liguori, 2008/10/10
- Re: [Qemu-devel] [RFC] Disk integrity in QEMU, Paul Brook, 2008/10/10
- Re: [Qemu-devel] [RFC] Disk integrity in QEMU, Anthony Liguori, 2008/10/10
- Re: [Qemu-devel] [RFC] Disk integrity in QEMU,
Paul Brook <=
- Re: [Qemu-devel] [RFC] Disk integrity in QEMU, Avi Kivity, 2008/10/10
- Re: [Qemu-devel] [RFC] Disk integrity in QEMU, Jens Axboe, 2008/10/17
- Re: [Qemu-devel] [RFC] Disk integrity in QEMU, Avi Kivity, 2008/10/19
- Re: [Qemu-devel] [RFC] Disk integrity in QEMU, Aurelien Jarno, 2008/10/10
Re: [Qemu-devel] [RFC] Disk integrity in QEMU, Avi Kivity, 2008/10/10
Re: [Qemu-devel] [RFC] Disk integrity in QEMU, Anthony Liguori, 2008/10/10