[Top][All Lists]

[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

Re: Priority of -accel (was: [PATCH] tests/qemu-iotests: Update tests to

From: Thomas Huth
Subject: Re: Priority of -accel (was: [PATCH] tests/qemu-iotests: Update tests to recent desugarized -accel option)
Date: Wed, 8 Jan 2020 11:58:47 +0100
User-agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.9.0

On 08/01/2020 11.39, Alex Bennée wrote:
> Thomas Huth <address@hidden> writes:
>> On 07/01/2020 13.54, Daniel P. Berrangé wrote:
>>> On Tue, Jan 07, 2020 at 01:23:18PM +0100, Paolo Bonzini wrote:
>>>> On 07/01/20 13:18, Thomas Huth wrote:
>>>>> I don't think we need a separate priority parameter here. But IMHO it's
>>>>>  really rather common practice to prioritize the last option. So while
>>>>> it might be more "self-explanatory" to a CLI newbie if the first
>>>>> occurrence got the highest priority, it might be rather confusing
>>>>> instead for a CLI veteran...?
>>>> Prioritising the last certainly makes sense for a choose-one-only
>>>> option, but I'm not sure it's the same for a choose-best option.  After
>>>> all it was -machine accel=kvm:tcg, not -machine accel=tcg:kvm...
>>> IIUC, the main use case for specifying multiple accelerators is
>>> so that lazy invokations can ask for a hardware virt, but then get
>>> fallback to TCG if not available. For things that should be platform
>>> portabile, there's more than just kvm to consider though, as we have
>>> many accelerators.  Listing all possible accelerators is kind of
>>> crazy though no matter what the syntax is.
>>> How about taking a completely different approach, inspired by the
>>> -cpu arg and implement:
>>>     -machine accel=best
>> Something like that sounds like the best solution to me, but I'd maybe
>> rather not call it "best", since the definition of "best" might depend
>> on your use-case (e.g. do you want to use a CPU close to the host or
>> something different which might be better emulated by TCG?).
> Indeed - you may well want to do TCG on Aarch64 if you want to test new
> instructions.
>> What about "-accel any" or "-accel fastest" or something similar?
> "any" is just ambiguous, "fastest" is just begging for me to find a
> micro-benchmark that TCG outperforms on ;-)
> "-accel default" could be considered to have vibes of Do The Right
> Thing (tm) and could in time actually become so!

"-accel default" sounds like the default behavior that you'd also get if
you don't use this option at all ... what about "-accel auto" to say
that QEMU should pick an accelerator automatically?


reply via email to

[Prev in Thread] Current Thread [Next in Thread]