[Intel-gfx] [PATCH 07/18] drm/i915: introduce ppgtt page coloring

[Chris Wilson]

On Wed, Apr 05, 2017 at 02:50:41PM +0100, Matthew Auld wrote:
> On 5 April 2017 at 14:41, Chris Wilson <chris at chris-wilson.co.uk> wrote:
> > On Tue, Apr 04, 2017 at 11:11:17PM +0100, Matthew Auld wrote:
> >> To enable 64K pages we need to set the intermediate-page-size(IPS) bit
> >> of the pde, therefore a page table is said to be either operating in 64K
> >> or 4K mode. To accommodate this vm placement restriction we introduce a
> >> color for pages and corresponding color_adjust callback.
> >>
> >> Signed-off-by: Matthew Auld <matthew.auld at intel.com>
> >> ---
> >>  drivers/gpu/drm/i915/i915_gem_gtt.c | 25 +++++++++++++++++++++++++
> >>  drivers/gpu/drm/i915/i915_gem_gtt.h |  6 ++++++
> >>  drivers/gpu/drm/i915/i915_vma.c     |  2 ++
> >>  3 files changed, 33 insertions(+)
> >>
> >> diff --git a/drivers/gpu/drm/i915/i915_gem_gtt.c b/drivers/gpu/drm/i915/i915_gem_gtt.c
> >> index 0989af4a17e4..ddc3db345b76 100644
> >> --- a/drivers/gpu/drm/i915/i915_gem_gtt.c
> >> +++ b/drivers/gpu/drm/i915/i915_gem_gtt.c
> >> @@ -1332,6 +1332,28 @@ static int gen8_preallocate_top_level_pdp(struct i915_hw_ppgtt *ppgtt)
> >>       return -ENOMEM;
> >>  }
> >>
> >> +static void i915_page_color_adjust(const struct drm_mm_node *node,
> >> +                                unsigned long color,
> >> +                                u64 *start,
> >> +                                u64 *end)
> >> +{
> >> +     GEM_BUG_ON(!is_valid_gtt_page_size(color));
> >> +
> >> +     if (!(color & (I915_GTT_PAGE_SIZE_4K | I915_GTT_PAGE_SIZE_64K)))
> >> +             return;
> >> +
> >> +     GEM_BUG_ON(node->allocated && !is_valid_gtt_page_size(node->color));
> >> +
> >> +     if (i915_node_color_differs(node, color))
> >> +             *start = roundup(*start, 1 << GEN8_PDE_SHIFT);
> >> +
> >> +     node = list_next_entry(node, node_list);
> >> +     if (i915_node_color_differs(node, color))
> >> +             *end = rounddown(*end, 1 << GEN8_PDE_SHIFT);
> >> +
> >> +     GEM_BUG_ON(node->allocated && !is_valid_gtt_page_size(node->color));
> >> +}
> >> +
> >>  /*
> >>   * GEN8 legacy ppgtt programming is accomplished through a max 4 PDP registers
> >>   * with a net effect resembling a 2-level page table in normal x86 terms. Each
> >> @@ -1372,6 +1394,9 @@ static int gen8_ppgtt_init(struct i915_hw_ppgtt *ppgtt)
> >>               ppgtt->base.allocate_va_range = gen8_ppgtt_alloc_4lvl;
> >>               ppgtt->base.insert_entries = gen8_ppgtt_insert_4lvl;
> >>               ppgtt->base.clear_range = gen8_ppgtt_clear_4lvl;
> >> +
> >> +             if (SUPPORTS_PAGE_SIZE(dev_priv, I915_GTT_PAGE_SIZE_64K))
> >> +                     ppgtt->base.mm.color_adjust = i915_page_color_adjust;
> >>       } else {
> >>               ret = __pdp_init(&ppgtt->base, &ppgtt->pdp);
> >>               if (ret)
> >> diff --git a/drivers/gpu/drm/i915/i915_gem_gtt.h b/drivers/gpu/drm/i915/i915_gem_gtt.h
> >> index 9c592e2de516..8d893ddd98f2 100644
> >> --- a/drivers/gpu/drm/i915/i915_gem_gtt.h
> >> +++ b/drivers/gpu/drm/i915/i915_gem_gtt.h
> >> @@ -353,6 +353,12 @@ i915_vm_has_cache_coloring(const struct i915_address_space *vm)
> >>  }
> >>
> >>  static inline bool
> >> +i915_vm_has_page_coloring(const struct i915_address_space *vm)
> >> +{
> >> +     return vm->mm.color_adjust && !i915_is_ggtt(vm);
> >> +}
> >> +
> >> +static inline bool
> >>  i915_vm_is_48bit(const struct i915_address_space *vm)
> >>  {
> >>       return (vm->total - 1) >> 32;
> >> diff --git a/drivers/gpu/drm/i915/i915_vma.c b/drivers/gpu/drm/i915/i915_vma.c
> >> index 8f0041ba328f..4043145b4310 100644
> >> --- a/drivers/gpu/drm/i915/i915_vma.c
> >> +++ b/drivers/gpu/drm/i915/i915_vma.c
> >> @@ -471,6 +471,8 @@ i915_vma_insert(struct i915_vma *vma, u64 size, u64 alignment, u64 flags)
> >>
> >>       if (i915_vm_has_cache_coloring(vma->vm))
> >>               color = obj->cache_level;
> >> +     else if (i915_vm_has_page_coloring(vma->vm))
> >> +             color = obj->gtt_page_size;
> >
> > This does not need color_adjust since you are just specifying an
> > alignment and size. Why the extra complications? I remember asking the
> > same last time.
> Hmm, are you saying the whole idea of needing a color_adjust for
> 4K/64K vm placement is completely unnecessary?

As constructed here, yes. Since you just want to request a
obj->gtt_page_size aligned block:

	.size = round_up(size, obj->gtt_page_size),
	.align = max(align, obj->gtt_page_size).

(Hmm, now I think about it you shouldn't round size up unless the
insert_pages() is careful not to assume that the last page is a full
superpage. More I think about this, you only want to align the base and
let insert_pages group up the superpages.)

Unless I have completely misunderstood, you do not need to insert
gaps between blocks. Both the color_adjust approach and this approach
still need lower level support to amalgamate pages.
-Chris

-- 
Chris Wilson, Intel Open Source Technology Centre