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Re: [Qemu-devel] Re: [PATCH] Add cache=volatile parameter to -drive
From: |
Jamie Lokier |
Subject: |
Re: [Qemu-devel] Re: [PATCH] Add cache=volatile parameter to -drive |
Date: |
Mon, 17 May 2010 21:07:43 +0100 |
User-agent: |
Mutt/1.5.13 (2006-08-11) |
Alexander Graf wrote:
>
> On 17.05.2010, at 18:26, Anthony Liguori wrote:
>
> > On 05/17/2010 11:23 AM, Paul Brook wrote:
> >>>> I don't see a difference between the results. Apparently the barrier
> >>>> option doesn't change a thing.
> >>>>
> >>> Ok. I don't like it, but I can see how it's compelling. I'd like to
> >>> see the documentation improved though. I also think a warning printed
> >>> on stdio about the safety of the option would be appropriate.
> >>>
> >> I disagree with this last bit.
> >>
> >> Errors should be issued if the user did something wrong.
> >> Warnings should be issued if qemu did (or will soon do) something other
> >> than
> >> what the user requested, or otherwise made questionable decisions on the
> >> user's behalf.
> >>
> >> In this case we're doing exactly what the user requested. The only
> >> plausible
> >> failure case is where a user is blindly trying options that they clearly
> >> don't
> >> understand or read the documentation for. I have zero sympathy for
> >> complaints
> >> like "Someone on the Internet told me to use --breakme, and broke thinks".
> >>
> >
> > I see it as the equivalent to the Taint bit in Linux. I want to make it
> > clear to users up front that if you use this option, and you have data loss
> > issues, don't complain.
> >
> > Just putting something in qemu-doc.texi is not enough IMHO. Few people
> > actually read it.
>
> But that's why it's no default and also called "volatile". If you prefer, we
> can call it cache=destroys_your_image.
With that semantic, a future iteration of cache=volatile could even
avoid writing to the backing file at all, if that's yet faster. I
wonder if that would be faster. Anyone fancy doing a hack with the
whole guest image as a big malloc inside qemu? I don't have enough RAM :-)
-- Jamie
- [Qemu-devel] Re: [PATCH] Add cache=volatile parameter to -drive, (continued)
- [Qemu-devel] Re: [PATCH] Add cache=volatile parameter to -drive, Alexander Graf, 2010/05/17
- [Qemu-devel] Re: [PATCH] Add cache=volatile parameter to -drive, Anthony Liguori, 2010/05/17
- [Qemu-devel] Re: [PATCH] Add cache=volatile parameter to -drive, Alexander Graf, 2010/05/17
- [Qemu-devel] Re: [PATCH] Add cache=volatile parameter to -drive, Anthony Liguori, 2010/05/17
- [Qemu-devel] Re: [PATCH] Add cache=volatile parameter to -drive, Alexander Graf, 2010/05/17
- Re: [Qemu-devel] Re: [PATCH] Add cache=volatile parameter to -drive, Alexander Graf, 2010/05/17
- [Qemu-devel] Re: [PATCH] Add cache=volatile parameter to -drive, Anthony Liguori, 2010/05/17
- Re: [Qemu-devel] Re: [PATCH] Add cache=volatile parameter to -drive, Paul Brook, 2010/05/17
- Re: [Qemu-devel] Re: [PATCH] Add cache=volatile parameter to -drive, Anthony Liguori, 2010/05/17
- Re: [Qemu-devel] Re: [PATCH] Add cache=volatile parameter to -drive, Alexander Graf, 2010/05/17
- Re: [Qemu-devel] Re: [PATCH] Add cache=volatile parameter to -drive,
Jamie Lokier <=
- Re: [Qemu-devel] Re: [PATCH] Add cache=volatile parameter to -drive, Kevin Wolf, 2010/05/18
- Re: [Qemu-devel] Re: [PATCH] Add cache=volatile parameter to -drive, Alexander Graf, 2010/05/25
- Re: [Qemu-devel] Re: [PATCH] Add cache=volatile parameter to -drive, Anthony Liguori, 2010/05/25
- Re: [Qemu-devel] Re: [PATCH] Add cache=volatile parameter to -drive, Alexander Graf, 2010/05/25
- Re: [Qemu-devel] Re: [PATCH] Add cache=volatile parameter to -drive, Avi Kivity, 2010/05/26
- Re: [Qemu-devel] Re: [PATCH] Add cache=volatile parameter to -drive, Aurelien Jarno, 2010/05/25
- Re: [Qemu-devel] Re: [PATCH] Add cache=volatile parameter to -drive, Anthony Liguori, 2010/05/25
- Re: [Qemu-devel] Re: [PATCH] Add cache=volatile parameter to -drive, Kevin Wolf, 2010/05/26
- Re: [Qemu-devel] Re: [PATCH] Add cache=volatile parameter to -drive, Anthony Liguori, 2010/05/26
- Re: [Qemu-devel] Re: [PATCH] Add cache=volatile parameter to -drive, Kevin Wolf, 2010/05/26