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

Alex Smith asmith at feralinteractive.com
Wed Jun 12 08:19:55 UTC 2019


On Tue, 11 Jun 2019 at 14:32, Christian K├Ânig <
ckoenig.leichtzumerken at gmail.com> wrote:

> Am 10.06.19 um 15:56 schrieb Bas Nieuwenhuizen:
> > On Sat, Jun 8, 2019 at 3:36 PM Alex Smith <asmith at feralinteractive.com>
> wrote:
> >> On Mon, 3 Jun 2019 at 13:27, Koenig, Christian <
> Christian.Koenig at amd.com> wrote:
> >>> Am 03.06.19 um 14:21 schrieb 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?
> >>>
> >>>
> >>> First of all take a look at amdgpu_gem_info file in the debugfs
> directory while using GTT and match that to using VRAM. You should see a
> lot more of GTT ... CPU_GTT_USWC entries with the GTT variant. If the
> CPU_GTT_USWC flag is missing we have found the problem.
> >>>
> >>> If that looks ok, then take a look at the ttm_page_pool or
> ttm_dma_page_pool file and see how many wc/uc and wc/uc huge pages you got.
> Huge pages should be used for anything larger than 2MB, if not we have
> found the problem.
> >>>
> >>> If that still isn't the issue I need to take a look at the VM code
> again and see if we still map VRAM/GTT differently on APUs.
> >>
> >> OK, got around to looking at this. amdgpu_gem_info does have more USWC
> entries when using GTT. I've attached the output from VRAM vs GTT in case
> you can spot anything else in there.
> >>
> >> ttm_page_pool has 9806 wc, 238 wc huge, no uc or uc huge.
> > To add to this, I tried rounding up the size all application GTT
> > allocations to a multiple of 2 megabytes (+ a suballocator for buffers
> > < 2M). This increased performance a bit but not nearly what going from
> > GTT->"VRAM" brings.
>
> I need to dig deeper when I have a bit more time.
>
> The logs Alex provided didn't showed anything obviously wrong, so no
> idea what's the actual problem here.
>
> Anyway feel free to go ahead with this approach, but please keep in mind
> that this might cause problems on some systems.
>

Thanks Christian.

Bas, Samuel - what do you think to going ahead with this change in the
meantime? Perhaps we could add some threshold on minimum "VRAM" size
(256MB?) required to change the order, to avoid issues on systems where
that heap is really small?

Alex


>
> Christian.
>
> >
> >> FWIW this was from kernel 5.0.10, I just upgraded to 5.1.6 and still
> the same perf difference there.
> >>
> >> Thanks,
> >> Alex
> >>
> >>>
> >>> Thanks,
> >>> Christian.
> >>>
> >>>
> >>> 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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