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Re: [Qemu-trivial] [Qemu-devel] [PATCH] kvm_irqchip_assign_irqfd: just s

From: Paolo Bonzini
Subject: Re: [Qemu-trivial] [Qemu-devel] [PATCH] kvm_irqchip_assign_irqfd: just set irqfd in case of kvm_irqfds_enabled()
Date: Sat, 27 Dec 2014 15:52:12 +0100
User-agent: Mozilla/5.0 (X11; Linux x86_64; rv:31.0) Gecko/20100101 Thunderbird/31.3.0

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...


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