On Fri, Dec 15, 2017 at 01:20:17PM +0000, Chris Wilson wrote: > A context encompasses the driver's view of process related state, and > encapsulates the logical GPU state where available. Each context is > currently equivalent to a process in CPU terms. Like with processes, > sometimes the user wants a lighter encapsulation that shares some state > with the parent process, for example two threads have unique register > state but share the virtual memory mappings. We can support exactly the > same principle using contexts where we may share the GTT but keep the > logical GPU state distinct. This allows quicker switching between those > contexts, and for userspace to allocate a single offset in the GTT and > use it across multiple contexts. Like with clone(), in the future we may > wish to allow userspace to select more features to copy across from the > parent, but for now we only allow sharing of the GTT. Our timelines are still per-vm and not per-ctx. This means that schedule() will have slightly unexpected behavior when dealing with two context of different priority sharing a VM. -Michał > > Note that if full per-process GTT is not supported on the harder, the > GTT are already implicitly shared between contexts, and this request > to create contexts with shared GTT fails. With full ppGTT, every fd > (i.e. every process) is allocated a unique GTT so this request cannot be > used to share GTT between processes/fds, it can only share GTT belonging > to this fd. > Testcase: igt/gem_ctx_shared > Signed-off-by: Chris Wilson <chris@xxxxxxxxxxxxxxxxxx> > Cc: Joonas Lahtinen <joonas.lahtinen@xxxxxxxxxxxxxxx> > Cc: Tvrtko Ursulin <tvrtko.ursulin@xxxxxxxxx> > Cc: Mika Kuoppala <mika.kuoppala@xxxxxxxxxxxxxxx> > Cc: Michał Winiarski <michal.winiarski@xxxxxxxxx> > --- > drivers/gpu/drm/i915/i915_gem_context.c | 62 ++++-- > drivers/gpu/drm/i915/i915_gem_gtt.c | 4 +- > drivers/gpu/drm/i915/i915_gem_gtt.h | 1 - > drivers/gpu/drm/i915/selftests/huge_pages.c | 1 - > drivers/gpu/drm/i915/selftests/i915_gem_context.c | 234 +++++++++++++++++----- > drivers/gpu/drm/i915/selftests/i915_gem_gtt.c | 1 - > drivers/gpu/drm/i915/selftests/mock_context.c | 2 +- > include/uapi/drm/i915_drm.h | 11 +- > 8 files changed, 241 insertions(+), 75 deletions(-) _______________________________________________ Intel-gfx mailing list Intel-gfx@xxxxxxxxxxxxxxxxxxxxx https://lists.freedesktop.org/mailman/listinfo/intel-gfx
