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Re: [Qemu-devel] Re: [PATCH] Add cache=volatile parameter to -drive
From: |
Kevin Wolf |
Subject: |
Re: [Qemu-devel] Re: [PATCH] Add cache=volatile parameter to -drive |
Date: |
Tue, 18 May 2010 09:42:03 +0200 |
User-agent: |
Mozilla/5.0 (X11; U; Linux x86_64; en-US; rv:1.9.1.9) Gecko/20100330 Fedora/3.0.4-1.fc12 Thunderbird/3.0.4 |
Am 17.05.2010 22:07, schrieb Jamie Lokier:
> 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 :-)
But then you'd probably want a separate RAM block driver instead of
messing with cache options.
Kevin
- [Qemu-devel] Re: [PATCH] Add cache=volatile parameter to -drive, (continued)
- [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, 2010/05/17
- Re: [Qemu-devel] Re: [PATCH] Add cache=volatile parameter to -drive,
Kevin Wolf <=
- 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
- Re: [Qemu-devel] Re: [PATCH] Add cache=volatile parameter to -drive, Anthony Liguori, 2010/05/26