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Re: [Qemu-devel] Re: [PATCH v3] introduce on_vcpu
From: |
Glauber Costa |
Subject: |
Re: [Qemu-devel] Re: [PATCH v3] introduce on_vcpu |
Date: |
Mon, 31 Aug 2009 09:14:28 -0300 |
User-agent: |
Jack Bauer |
On Mon, Aug 31, 2009 at 01:04:52PM +0100, Jamie Lokier wrote:
> Glauber Costa wrote:
> > 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.
>
> I was going to say just use pthread_self()! It's fast like TLS on all
> hosts, and more portable then gettid().
>
> But then you mentioned signals. I'm not sure if the code in question
> is inside signal handlers.
Signals are just used to wake up the other cpu. I think it is pretty valid
to rule out usage insigne signal handlers (mention in comments, etc).
I'll propose that switch on qemu-kvm, which already uses tls variables, and see
what the response is.
- [Qemu-devel] Re: [PATCH v3] introduce on_vcpu, Jan Kiszka, 2009/08/27
- [Qemu-devel] Re: [PATCH v3] introduce on_vcpu, Glauber Costa, 2009/08/27
- [Qemu-devel] Re: [PATCH v3] introduce on_vcpu, Glauber Costa, 2009/08/27
- [Qemu-devel] Re: [PATCH v3] introduce on_vcpu, Anthony Liguori, 2009/08/27
- [Qemu-devel] Re: [PATCH v3] introduce on_vcpu, Glauber Costa, 2009/08/27
- Re: [Qemu-devel] Re: [PATCH v3] introduce on_vcpu, Gleb Natapov, 2009/08/28
- Re: [Qemu-devel] Re: [PATCH v3] introduce on_vcpu, Jamie Lokier, 2009/08/28
- Re: [Qemu-devel] Re: [PATCH v3] introduce on_vcpu, Glauber Costa, 2009/08/31
- Re: [Qemu-devel] Re: [PATCH v3] introduce on_vcpu, Jamie Lokier, 2009/08/31
- Re: [Qemu-devel] Re: [PATCH v3] introduce on_vcpu,
Glauber Costa <=
- Re: [Qemu-devel] Re: [PATCH v3] introduce on_vcpu, Jan Kiszka, 2009/08/31
- Re: [Qemu-devel] Re: [PATCH v3] introduce on_vcpu, Jamie Lokier, 2009/08/31
- Re: [Qemu-devel] Re: [PATCH v3] introduce on_vcpu, Glauber Costa, 2009/08/31
- [Qemu-devel] Re: [PATCH v3] introduce on_vcpu, Paolo Bonzini, 2009/08/31