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Date: Mon, 29 Dec 2014 09:31:30 +0800
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Subject: Re: [Qemu-devel] [PATCH] kvm_irqchip_assign_irqfd: just set irqfd
 in case of kvm_irqfds_enabled()
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To: Paolo Bonzini <pbonzini@redhat.com>, Peter Maydell <peter.maydell@linaro.org>, "Denis V. Lunev" <den-lists@parallels.com>
Cc: QEMU Trivial <qemu-trivial@nongnu.org>, QEMU Developers <qemu-devel@nongnu.org>, kvm-devel <kvm@vger.kernel.org>


On 2014/12/27 22:52, Paolo Bonzini wrote:
>
>
> On 26/12/2014 18:59, Peter Maydell wrote:
>> Mm, but once you're into such microoptimisations as this you really
>> need to have a good justification for the effort, in the form of
>> profiling measurements that indicate that this is a hot path.
>> In this case that seems pretty unlikely, because I'd expect all
>> the systems where we care about performance will support irqfds,
>> so we won't be taking the early-exit code path anyhow. (And
>> not supporting irqfds is leaving much more performance on the
>> table than we could possibly be talking about in this function.)
>
> Also, it's even possible for a compiler to figure this out.  All in all,
> I don't see any advantage to this patch...
>

Indeed, its just a cleanup to make codes readable and comprehensible 
since oftentimes we don't initially write such a subsequent code just 
because we have this possibility to figure them out by the compiler, or 
others. And this is why I'm CCing Qemu trivial.

Tiejun