On Tue, Sep 29, 2015 at 09:01:33 +0200, Jakub Jelinek wrote:
> On Mon, Sep 28, 2015 at 05:53:42PM +0300, Ilya Verbin wrote:
> > Currently the COI emulator is single-threaded, i.e. it is able to run only
> > one
> > target function at a time, e.g. the following testcase:
> >
> > #pragma omp parallel sections num_threads(2)
> > {
> > #pragma omp section
> > #pragma omp target
> > while (1)
> > putchar ('.');
> >
> > #pragma omp section
> > #pragma omp target
> > while (1)
> > putchar ('o');
> > }
> >
> > prints only dots using emul, while using real libcoi it prints:
> > ...o.ooooo.o.o...o...o....oooo.oo.o.....o.ooo.oooooo...o.ooooooooo.o...o.ooooooo
> > Of course, it's not possible to test new OpenMP 4.1's async features using
> > such
> > an emulator.
> >
> > The patch bellow makes it asynchronous, it creates an auxiliary thread for
> > each
> > COIPipeline in host and in target processes. In general, a new COIPipeline
> > is
> > created by liboffloadmic for each host thread with offload, i.e. the example
> > above has:
> > 4 threads in the host process (2 OpenMP threads + 2 auxiliary threads) and
> > 3 threads in the target process (1 main thread + 2 auxiliary threads).
> > An auxiliary host thread runs a target function in the new thread in target
> > process and waits for its completion. When the function is finished, the
> > host
> > thread signals an event and can run a callback, if it is registered.
> > liboffloadmic waits for signalled events by calling COIEventWait.
> > This is identical to how real libcoi works.
> >
> > make check-target-libgomp and some internal tests did not show any
> > regression.
> > TSan report is clean. Is it OK for trunk?
>
> For now ok. Though, I'd say I'd prefer if there were no auxiliary threads
> on the host side, just whatever thread is asked to send something to/from
> the device, wait for something and/or poll for something just polling the
>
> pipes. Are there auxiliary host threads also for the case when using
> the real COI, offloading to hw?
Yes.
-- Ilya
