[Mesa-dev] [PATCH] radv: Change memory type order for GPUs without dedicated VRAM

[Alex Smith]

On Mon, 3 Jun 2019 at 11:57, Koenig, Christian <Christian.Koenig at amd.com>
wrote:

> Am 02.06.19 um 12:32 schrieb Alex Smith:
> > Put the uncached GTT type at a higher index than the visible VRAM type,
> > rather than having GTT first.
> >
> > When we don't have dedicated VRAM, we don't have a non-visible VRAM
> > type, and the property flags for GTT and visible VRAM are identical.
> > According to the spec, for types with identical flags, we should give
> > the one with better performance a lower index.
> >
> > Previously, apps which follow the spec guidance for choosing a memory
> > type would have picked the GTT type in preference to visible VRAM (all
> > Feral games will do this), and end up with lower performance.
> >
> > On a Ryzen 5 2500U laptop (Raven Ridge), this improves average FPS in
> > the Rise of the Tomb Raider benchmark by up to ~30%. Tested a couple of
> > other (Feral) games and saw similar improvement on those as well.
>
> Well that patch doesn't looks like a good idea to me.
>
> Using VRAM over uncached GTT should have something between no and only
> minimal performance difference on APU.
>
> To make things even worse VRAM is still needed for scanout and newer
> laptops have only a very very low default setting (32 or 16MB). So you
> can end up in VRAM clashing on those systems.
>
> Can you check some kernel statistics to figure out what exactly is going
> on here?
>

What statistics should I look at?

Thanks,
Alex


>
> Regards,
> Christian.
>
> >
> > Signed-off-by: Alex Smith <asmith at feralinteractive.com>
> > ---
> > I noticed that the memory types advertised on my Raven laptop looked a
> > bit odd so played around with it and found this. I'm not sure if it is
> > actually expected that the performance difference between visible VRAM
> > and GTT is so large, seeing as it's not dedicated VRAM, but the results
> > are clear (and consistent, tested multiple times).
> > ---
> >   src/amd/vulkan/radv_device.c | 18 +++++++++++++++---
> >   1 file changed, 15 insertions(+), 3 deletions(-)
> >
> > diff --git a/src/amd/vulkan/radv_device.c b/src/amd/vulkan/radv_device.c
> > index 3cf050ed220..d36ee226ebd 100644
> > --- a/src/amd/vulkan/radv_device.c
> > +++ b/src/amd/vulkan/radv_device.c
> > @@ -171,12 +171,11 @@ radv_physical_device_init_mem_types(struct
> radv_physical_device *device)
> >                       .heapIndex = vram_index,
> >               };
> >       }
> > -     if (gart_index >= 0) {
> > +     if (gart_index >= 0 && device->rad_info.has_dedicated_vram) {
> >               device->mem_type_indices[type_count] =
> RADV_MEM_TYPE_GTT_WRITE_COMBINE;
> >               device->memory_properties.memoryTypes[type_count++] =
> (VkMemoryType) {
> >                       .propertyFlags =
> VK_MEMORY_PROPERTY_HOST_VISIBLE_BIT |
> > -                     VK_MEMORY_PROPERTY_HOST_COHERENT_BIT |
> > -                     (device->rad_info.has_dedicated_vram ? 0 :
> VK_MEMORY_PROPERTY_DEVICE_LOCAL_BIT),
> > +                     VK_MEMORY_PROPERTY_HOST_COHERENT_BIT,
> >                       .heapIndex = gart_index,
> >               };
> >       }
> > @@ -189,6 +188,19 @@ radv_physical_device_init_mem_types(struct
> radv_physical_device *device)
> >                       .heapIndex = visible_vram_index,
> >               };
> >       }
> > +     if (gart_index >= 0 && !device->rad_info.has_dedicated_vram) {
> > +             /* Put GTT after visible VRAM for GPUs without dedicated
> VRAM
> > +              * as they have identical property flags, and according to
> the
> > +              * spec, for types with identical flags, the one with
> greater
> > +              * performance must be given a lower index. */
> > +             device->mem_type_indices[type_count] =
> RADV_MEM_TYPE_GTT_WRITE_COMBINE;
> > +             device->memory_properties.memoryTypes[type_count++] =
> (VkMemoryType) {
> > +                     .propertyFlags =
> VK_MEMORY_PROPERTY_DEVICE_LOCAL_BIT |
> > +                     VK_MEMORY_PROPERTY_HOST_VISIBLE_BIT |
> > +                     VK_MEMORY_PROPERTY_HOST_COHERENT_BIT,
> > +                     .heapIndex = gart_index,
> > +             };
> > +     }
> >       if (gart_index >= 0) {
> >               device->mem_type_indices[type_count] =
> RADV_MEM_TYPE_GTT_CACHED;
> >               device->memory_properties.memoryTypes[type_count++] =
> (VkMemoryType) {
>
>
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