Re: [PATCH v2 2/6] accel: accel_available() function

[Claudio Fontana <cfontana@suse.de>]

On 11/26/20 10:48 PM, Eduardo Habkost wrote:
> On Thu, Nov 26, 2020 at 10:06:03PM +0100, Claudio Fontana wrote:
>> On 11/26/20 3:25 PM, Paolo Bonzini wrote:
>>> On 26/11/20 15:13, Claudio Fontana wrote:
>>>> One option I see is simply to document the behavior where
>>>> accel_available() is declared in accel.h (ie do not use in fast
>>>> path), as well as in accel_find() actually, so that both accel_find()
>>>> and accel_available() are avoided in fast path and avoid being called
>>>> frequently at runtime.
>>>>
>>>> Another option could be to remove the allocation completely, and use
>>>> for example accel_find(ACCEL_CLASS_NAME("tcg")), or another option
>>>> again would be to remove the allocation and use either a fixed buffer
>>>> + snprintf, or alloca -like builtin code to use the stack, ...
>>>>
>>>> Not a big deal, but with a general utility and short name like
>>>> accel_available(name) it might be tempting to use this more in the
>>>> future?
>>>
>>> I think it's just that the usecase is not that common.  "Is this 
>>> accelerator compiled in the binary" is not something you need after 
>>> startup (or if querying the monitor).
>>>
>>> Paolo
>>>
>>>
>>
>> A script that repeatedly uses the QMP interface to query for
>> the status could generate fragmentation this way I think.
> 
> Is this a problem?  Today, execution of a "query-kvm" command
> calls g_malloc() 37 times.
> 

Not ideal in my view, but not the end of the world either.

Ciao,

Claudio