Re: [Qemu-devel] [PATCH] qemu-thread: add TLS wrappers

[malc]

On Wed, 17 Aug 2011, Paolo Bonzini wrote:

> On 08/17/2011 10:51 AM, Blue Swirl wrote:
> > >  Visual C++ supports __declspec(thread).
> > >
> > >  pthread TLS is orders of magnitudes slower than __thread.  __thread in an
> > >  executable is just as fast as a non-TLS variable access, 2 or 3 machine
> > >  language instructions at most.
> > >
> > >  Some pthread_getspecific implementation do a_linear walk_  of the keys.
> > In
> > >  that case it may work to have something like Windows plus a single
> > >  pthread_getspecific key.  On the other hand, Windows provides very good
> > >  support for that thanks to its ordered subsections (.tls$something).  It
> > >  only needs a bit of preprocessor magic.  Thinks such as linker scripts
> > would
> > >  be way out of scope.
> > 
> > According to this blog, also pthread_getspecific on OSX can amount to
> > three instructions except on PPC:
> > http://lifecs.likai.org/2010/05/mac-os-x-thread-local-storage.html
> 
> I'll try to work out a DEFINE_TLS/DECLARE_TLS version for pthreads too.
> 
> BTW, __thread is in C1X too though I don't remember how they called it.
> 

thread_local 3.7.2 in n3290.pdf

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