On Thu, Apr 14, 2016 at 12:24:20PM +0100, Tvrtko Ursulin wrote: > > On 14/04/16 12:16, Chris Wilson wrote: > >On Thu, Apr 14, 2016 at 11:59:29AM +0100, Tvrtko Ursulin wrote: > >>From: Tvrtko Ursulin <tvrtko.ursulin@xxxxxxxxx> > >> > >>We know ringbuffers are memory and not ports so if we use readl > >>and writel instead of ioread32 and iowrite32 (which dispatch to > >>the very same functions after checking the address range) we > >>avoid generating functions calls and branching on every access. > > > >We don't need to use readl/write at all, since they are normal memory > >on llc, and on x86 we can pretend that iomaps (!llc/stolen) are as well. > > It is fine to use readl/writel since it translates to a single mov > instruction anyway on x86. > > >This patch is in the queue along with killing the incorrect spare iomem > >annotation. > > Ok did not spot them. Don't mind either way, thought this is quick, > easy and obvious improvement when I spotted the ugly code generated > for ring buffer writing. > > Mind you it is still not completely pretty with this patch since it > is full of reloads and adds for ringbuf->virtual_start and tail > which I can't figure how to help GCC optimize. Unless we make being, > emit and advance functions return the current tail pointer and also > accept it. In that case it all shrinks by half. We figured out how to help gcc with that in userspace using: out = ring_begin(num_dwords); out[0] = cmd; out[N] = dwN GCC will then do mov $imm0, 0x0($eax) mov $imm1, 0x4($eax) mov $edx, 0x8($eax) etc Forgive the clumsy rebasing: https://cgit.freedesktop.org/~ickle/linux-2.6/commit/?h=tasklet&id=a5c7b28441af0cb0e640f4ba86facba69e8f6c37 drivers/gpu/drm/i915/i915_gem.c | 4 - drivers/gpu/drm/i915/i915_gem_context.c | 76 +-- drivers/gpu/drm/i915/i915_gem_execbuffer.c | 37 +- drivers/gpu/drm/i915/i915_gem_gtt.c | 61 +- drivers/gpu/drm/i915/i915_gem_request.c | 121 +++- drivers/gpu/drm/i915/i915_gem_request.h | 3 + drivers/gpu/drm/i915/i915_guc_submission.c | 2 +- drivers/gpu/drm/i915/intel_display.c | 134 ++--- drivers/gpu/drm/i915/intel_lrc.c | 239 ++++---- drivers/gpu/drm/i915/intel_mocs.c | 50 +- drivers/gpu/drm/i915/intel_overlay.c | 77 +-- drivers/gpu/drm/i915/intel_ringbuffer.c | 922 ++++++++++++----------------- drivers/gpu/drm/i915/intel_ringbuffer.h | 28 +- 13 files changed, 793 insertions(+), 961 deletions(-) -Chris -- Chris Wilson, Intel Open Source Technology Centre _______________________________________________ Intel-gfx mailing list Intel-gfx@xxxxxxxxxxxxxxxxxxxxx https://lists.freedesktop.org/mailman/listinfo/intel-gfx
