[Top][All Lists]
[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]
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: |
Wed, 26 May 2010 16:26:00 +0200 |
User-agent: |
Mozilla/5.0 (X11; U; Linux x86_64; en-US; rv:1.9.1.9) Gecko/20100430 Fedora/3.0.4-2.fc12 Thunderbird/3.0.4 |
Am 26.05.2010 16:08, schrieb Anthony Liguori:
> On 05/26/2010 09:03 AM, Kevin Wolf wrote:
>> Am 26.05.2010 15:42, schrieb Anthony Liguori:
>>
>>> On 05/26/2010 03:43 AM, Kevin Wolf wrote:
>>>
>>>> Am 26.05.2010 03:31, schrieb Anthony Liguori:
>>>>
>>>>
>>>>> On 05/25/2010 04:01 PM, Aurelien Jarno wrote:
>>>>>
>>>>>
>>>>>> I really think this patch can be useful, in my own case when testing
>>>>>> debian-installer (I already cache=writeback). In short all that is about
>>>>>> developing and testing, as opposed to run a VM in production, can
>>>>>> benefit about that. This was one of the original use case of QEMU before
>>>>>> KVM arrived.
>>>>>>
>>>>>> Unless someone can convince me not to do it, I seriously considering
>>>>>> applying this patch.
>>>>>>
>>>>>>
>>>>>>
>>>>> There really needs to be an indication in the --help output of what the
>>>>> ramifications of this option are, in the very least. It should also be
>>>>> removable via a ./configure option because no sane distribution should
>>>>> enable this for end users.
>>>>>
>>>>>
>>>> We know better what you stupid user want?
>>>>
>>> What percentage of qemu users do you think have actually read qemu-doc.texi?
>>>
>> As I said, put the warning in the option name like cache=unsafe or
>> something even more scary and I'm all for it.
>>
>>
>>> It's not a stretch for someone to have heard that cache options can
>>> improve performance, and then see cache=volatile in the help output, try
>>> it, and then start using it because they observe a performance improvement.
>>>
>>> That's not being stupid. I think it's a reasonable expectation for a
>>> user to have that their data is safe.
>>>
>> You seem to think that the user is too stupid to allow him to use this
>> option even if he's perfectly aware what it's doing. It's a useful
>> option if it's used right.
>>
>
> No, that's not what I said. I'm saying we need to try hard to make a
> user aware of what they're doing.
>
> If it spit out a warning on stdio, I wouldn't think a compile option is
> needed. Even with help output text, I'm concerned that someone is going
> to find a bad example on the internet.
>
> cache=unsafe addresses the problem although I think it's a bit hokey.
Then let's do it this way. I'm not opposed to a stdio message either,
even though I don't think it's really necessary with a name like
cache=unsafe. I just say that disabling the option is not a solution
because it prevents valid use.
>> We need to make clear that it's dangerous when it's used in the wrong
>> cases (for example by naming), but just disabling is not a solution for
>> that. You don't suggest that "no sane distribution" should ship rm,
>> because it's dangerous if you use it wrong, do you?
>>
>
> You realize that quite a lot of distributions carry a patch to rm that
> prevents a user from doing rm -rf /?
Most rm invocations that I regretted later were not rm -rf /. Actually,
I think rm -rf / is not among them at all. ;-)
And I seem to remember that even these rm patches still allow the
protection to be overridden by some force flag. But I've never tried it out.
Kevin
- Re: [Qemu-devel] Re: [PATCH] Add cache=volatile parameter to -drive, (continued)
- 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
- Re: [Qemu-devel] Re: [PATCH] Add cache=volatile parameter to -drive,
Kevin Wolf <=
- Re: [Qemu-devel] Re: [PATCH] Add cache=volatile parameter to -drive, Aurelien Jarno, 2010/05/26
- Re: [Qemu-devel] Re: [PATCH] Add cache=volatile parameter to -drive, Aurelien Jarno, 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
- [Qemu-devel] Re: [PATCH] Add cache=volatile parameter to -drive, Paolo Bonzini, 2010/05/26
- Re: [Qemu-devel] Re: [PATCH] Add cache=volatile parameter to -drive, Aurelien Jarno, 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, Aurelien Jarno, 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, Avi Kivity, 2010/05/26