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Date: Mon, 31 Aug 2009 08:35:18 -0300
From: Glauber Costa <glommer@redhat.com>
Subject: Re: [Qemu-devel] Re: [PATCH v3] introduce on_vcpu
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To: Jamie Lokier <jamie@shareable.org>
Cc: Jan Kiszka <jan.kiszka@siemens.com>, Anthony Liguori <aliguori@us.ibm.com>, qemu-devel@nongnu.org, avi@redhat.com

On Sat, Aug 29, 2009 at 02:22:27AM +0100, Jamie Lokier wrote:
> Anthony Liguori wrote:
> > Glauber Costa wrote:
> > Since we already keep the tid in the vcpu structure, it seems to make 
> > more sense to ask "am I this vcpu thread" by doing gettid() == env->tid 
> > than by maintaining a new global tls variable.
> 
> Note that a tls variable will be much faster than gettid().  Don't
> know if you're talking about a hot path.
just to be sure, TLS is not supported on all our linux target hosts, right?

We can probably wrap it into a function that uses gettid on linux (or whatever
in other platforms), and uses a TLS variable where available. (and if needed).

I can agree with anthony that although TLS is in fact faster, we might not need it.
I doubt that anything that communicates using signals will be the hot path for anything.