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Re: [Qemu-devel] Should we auto-generate IDs?
From: |
Programmingkid |
Subject: |
Re: [Qemu-devel] Should we auto-generate IDs? |
Date: |
Wed, 26 Aug 2015 14:17:17 -0400 |
On Aug 26, 2015, at 2:08 PM, Jeff Cody wrote:
> On Wed, Aug 26, 2015 at 01:29:04PM -0400, Programmingkid wrote:
>>
>> On Aug 26, 2015, at 1:25 PM, Jeff Cody wrote:
>>
>>> On Wed, Aug 26, 2015 at 06:31:57PM +0200, Markus Armbruster wrote:
>>>> Did you drop cc's intentionally? I put them right back.
>>>>
>>>> Programmingkid <address@hidden> writes:
>>>>
>>>>> On Aug 25, 2015, at 8:38 AM, Markus Armbruster wrote:
>>>>>
>>>>>> You're proposing to revise a qdev design decision, namely the purpose of
>>>>>> IDs. This has been discussed before, and IDs remained unchanged.
>>>>>> Perhaps it's time to revisit this issue. Cc'ing a few more people.
>>>>>>
>>>>>> Relevant prior threads:
>>>>>> * [PATCH] qdev: Reject duplicate and anti-social device IDs
>>>>>> http://thread.gmane.org/gmane.comp.emulators.qemu/71230/focus=72272
>>>>>> * [PATCH 6/6] qdev: Generate IDs for anonymous devices
>>>>>> http://thread.gmane.org/gmane.comp.emulators.qemu/114853/focus=114858
>>>>>> * [PATCH] qdev: Assign a default device ID when none is provided.
>>>>>> http://thread.gmane.org/gmane.comp.emulators.qemu/249702
>>>>>> * IDs in QOM (was: [PATCH] util: Emancipate id_wellformed() from QemuOpt
>>>>>> http://thread.gmane.org/gmane.comp.emulators.qemu/299945/focus=300381
>>>>>>
>>>>>
>>>>> After reading all the threads, I realize why all the attempts to
>>>>> accept a device ID patch failed.
>>>>> It is because it was assumed everyone would agree on one patch to
>>>>> accept. This is
>>>>> very unlikely. It would take someone in a leadership position to
>>>>> decide which patch
>>>>> should be accepted. From one of the threads above, I saw Anthony
>>>>> Liguori participate.
>>>>> He was in the perfect position to make the choice. The person who is
>>>>> in his position now
>>>>> is Peter Maydell. Maybe we should just ask him to look at all the
>>>>> candidate patches and
>>>>> have him pick one to use.
>>>>
>>>> Yes, when no consensus emerges, problems tend to go unsolved.
>>>>
>>>> Before we appeal to authority to break the deadlock, we should make
>>>> another attempt at finding consensus.
>>>>
>>>> I know that we've entertained the idea of automatically generated IDs
>>>> for block layer objects (that's why I cc'ed some block guys).
>>>
>>> Yeah, I was one of the ones that proposed some auto-generated IDs for
>>> the block layer, specifically for BlockDriverState, making use of the
>>> node-name field that Benoit introduced a while ago. Here is my patch
>>> (not sure if this is the latest version, but it is sufficient for this
>>> discussion):
>>>
>>> http://patchwork.ozlabs.org/patch/355990/
>>>
>>> I'm not sure about the requirements needed by device ID names, and
>>> they may of course differ from what I was thinking for BDS entries.
>>>
>>> Here is what I was after with my patch for node-name auto-generation:
>>>
>>> * Identifiable as QEMU generated / reserved namespace
>>>
>>> * Guaranteed uniqueness
>>>
>>> * Non-predictable (don't want users trying to guess / assume
>>> generated node-names)
>>>
>>> My approach was overkill in some ways (24 characters!). But for
>>> better or worse, what I had was:
>>>
>>> __qemu##00000000IAIYNXXR
>>> ^^^^^^^^
>>> QEMU namespace ----| ^^^^^^^^
>>> | ^^^^^^^^^
>>> Increment counter, unique | |
>>> |
>>> Random string, to spoil prediction |
>>
>> Yikes! 24 characters long. That is a bit much to type. Thank you very much
>> for your effort.
>
> IMO, the number of characters to type is pretty low on the list of
> requirements, although it can still be addressed secondary to other
> concerns.
>
> I should have made this in reply to Markus' other email, because the
> important part of this is try and address his point #2:
>
> (from Markus' other email):
>> 2. The ID must be well-formed.
>
> To have a well-formed ID, we need to have know requirements of the ID
> structure (i.e. the why and what of it all)
>
> I don't know if the three requirements I had above apply to all areas
> in QEMU, but I expect they do, in varying degrees of importance. The
> length itself can be tweaked.
>
> Talking with John Snow over IRC (added to the CC), one thing he
> suggested was adding in sub-domain spaces; e.g.:
>
> __qemu#bn#00000000#IAIYNXXR
>
> Where the 'bn' in this case would be for Block Nodes, etc..
>
> This may make the scheme extensible through QEMU, where auto-generated
> IDs are desired.
>
> (sorry to say, this lengthens things, rather than shortening them!)
>
> We can, of course, make the string shorter - if the random characters
> are just there for spoiling predictability, then 2-3 should be
> sufficient. We could then end up with something like this:
>
> __qemu#bn#00000000#XR
>
> The "__qemu" part of the namespace could be shortened as well, but it
> would be nice if it was easy recognizable as being from QEMU.
If this ID format was supported, I'm thinking being able to copy and paste from
the monitor is a necessary feature.
Any way it could be shorted? I was hoping no more than three characters long.
If this were the format of the ID, maybe we could put the value in a table that
would translate this long ID to a shorter version. Or maybe a mathematical
function
could be applied to the value to give it some user-friendly value.
I do think your idea virtually eliminates the problem of ID collisions.
- Re: [Qemu-devel] Should we auto-generate IDs?, (continued)
- Re: [Qemu-devel] Should we auto-generate IDs?, Markus Armbruster, 2015/08/26
- Re: [Qemu-devel] Should we auto-generate IDs?, Programmingkid, 2015/08/26
- Re: [Qemu-devel] Should we auto-generate IDs?, Peter Maydell, 2015/08/26
- Re: [Qemu-devel] Should we auto-generate IDs?, Programmingkid, 2015/08/26
- Re: [Qemu-devel] Should we auto-generate IDs?, John Snow, 2015/08/26
- Re: [Qemu-devel] Should we auto-generate IDs?, Programmingkid, 2015/08/26
- Re: [Qemu-devel] Should we auto-generate IDs?, Markus Armbruster, 2015/08/27
- Re: [Qemu-devel] Should we auto-generate IDs?, Jeff Cody, 2015/08/26
- Re: [Qemu-devel] Should we auto-generate IDs?, Programmingkid, 2015/08/26
- Re: [Qemu-devel] Should we auto-generate IDs?, Jeff Cody, 2015/08/26
- Re: [Qemu-devel] Should we auto-generate IDs?,
Programmingkid <=
- Re: [Qemu-devel] Should we auto-generate IDs?, Jeff Cody, 2015/08/26
- Re: [Qemu-devel] Should we auto-generate IDs?, John Snow, 2015/08/26
- Re: [Qemu-devel] Should we auto-generate IDs?, Programmingkid, 2015/08/26
- Re: [Qemu-devel] Should we auto-generate IDs?, Programmingkid, 2015/08/26
- Re: [Qemu-devel] Should we auto-generate IDs?, Jeff Cody, 2015/08/27
- Re: [Qemu-devel] Should we auto-generate IDs?, Eric Blake, 2015/08/27
- Re: [Qemu-devel] Should we auto-generate IDs?, Programmingkid, 2015/08/27
- Re: [Qemu-devel] Should we auto-generate IDs?, Daniel P. Berrange, 2015/08/27
- Re: [Qemu-devel] Should we auto-generate IDs?, Eric Blake, 2015/08/27
- Re: [Qemu-devel] Should we auto-generate IDs?, Jeff Cody, 2015/08/27