On Tue, Mar 22, 2011 at 03:41:19PM -0500, Timothy Baldridge wrote: > After my last discussion about getting some multi-threading > primitives, I took a look at how locks are implemented in PyPy. PyPy > currently uses OS level mutexes...which is okay for most uses, but in > my case, I need super fast spinlocks, and for that I need a CAS > operation. What I'm looking for is a bit of direction on how to go > about implementing this function (shown in C syntax): > > int cas(*expected, *new, **location) > > This function looks at the contents of the data pointed at by > **location. If the contents == *expected, the contents are replaced > with *new and the function returns true. Otherwise the function > returns false. > > There are several issues I see with implementing this in python: > > 1) **location must be pointer to a object pointer, is this even > possible in PyPy? > 2) I'd rather not call an FFI C function for this, when this entire > function could be inlined with just a few lines of assembly (CAS is a > single instruction on x86). So could this be created as a C function > that is simply inserted into the generated C code, so that GCC could > inline it at will? > > I'm just brainstorming here. No matter how you dice it, CAS is pretty > much a prerequisite to any sort of multi-threaded programming these > days. That is unless you want to spend thousands of clock cycles in > context switches. > > Timothy > > -- > “One of the main causes of the fall of the Roman Empire was > that–lacking zero–they had no way to indicate successful termination > of their C programs.” > (Robert Firth) > _______________________________________________ > pypy-dev@codespeak.net > http://codespeak.net/mailman/listinfo/pypy-dev
Dont know if this would be helpful at all but i have been wondering if RCU's would be useful at all http://en.wikipedia.org/wiki/Read-copy-update (userspace libary at http://lttng.org/urcu ) from what i ahve read up on them i thought they would be a nice match to python and pypy _______________________________________________ pypy-dev@codespeak.net http://codespeak.net/mailman/listinfo/pypy-dev
