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Date: Fri, 28 Aug 2009 09:18:47 +0300
From: Gleb Natapov <gleb@redhat.com>
Subject: Re: [Qemu-devel] Re: [PATCH v3] introduce on_vcpu
Message-ID: <20090828061846.GA22585@redhat.com>
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To: Anthony Liguori <aliguori@us.ibm.com>
Cc: Jan Kiszka <jan.kiszka@siemens.com>, Glauber Costa <glommer@redhat.com>, qemu-devel@nongnu.org, avi@redhat.com

On Thu, Aug 27, 2009 at 08:38:56PM -0500, Anthony Liguori wrote:
> Glauber Costa wrote:
> >qemu-kvm uses a TLS variable for that, to guarantee that we're in the same thread
> >as our calling context. I like this idea. if we have io-thread disabled, we're always
> >in the same thread, and will always execute the function directly as we used to do
> >before on_vcpu().
> >
> >I do however remember anthony bending towards issuing a gettid() instead of using
> >a TLS var. I'm fine with both. Anthony, avi, you guys have a word here?
> 
> 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.
> 
What is the problem with tls variables? Why do unneeded system call?

--
			Gleb.