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

From: Chen, Tiejun
Subject: Re: [Qemu-trivial] [Qemu-devel] [PATCH] kvm_irqchip_assign_irqfd: just set irqfd in case of kvm_irqfds_enabled()
Date: Mon, 29 Dec 2014 09:31:30 +0800
User-agent: Mozilla/5.0 (Windows NT 6.1; WOW64; rv:31.0) Gecko/20100101 Thunderbird/31.3.0

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.


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