[PATCH] drm/amdgpu: Adjust logic around GTT size
Alex Deucher
alexdeucher at gmail.com
Sun May 22 23:36:30 UTC 2022
On Sun, May 22, 2022 at 4:03 AM Christian König
<ckoenig.leichtzumerken at gmail.com> wrote:
>
> Well, it's not arguing. I'm just pointing out the problems.
>
> Those issues were discovered because I'm trying to raise the limit for a couple of years now.
I think simply retesting the problematic tests on a modern system
should be enough. The old limit was put in place in the Carrizo
timeframe. Back then boards generally only had 2-4G of system memory.
Alex
>
> I've also already hacked together the necessary functionality, but upstreaming them has caused other issues which I don't have time to solve.
>
> If you have time to tackle those, I'm happy to push the necessary patches upstream.
>
> Regards,
> Christian.
>
> Am 20.05.22 um 23:36 schrieb Marek Olšák:
>
> We don't have to care about case 2 here. Broken apps will be handled by app profiles. The problem is that some games don't work with the current limit on the most powerful consumer APU we've ever made (Rembrandt) with precisely the games that the APU was made for, and instead of increasing the limit, we continue arguing about some TTM stuff that doesn't help anything right now.
>
> Marek
>
> On Fri., May 20, 2022, 14:25 Christian König, <ckoenig.leichtzumerken at gmail.com> wrote:
>>
>> Am 20.05.22 um 19:41 schrieb Bas Nieuwenhuizen:
>> > On Fri, May 20, 2022 at 11:42 AM Christian König
>> > <ckoenig.leichtzumerken at gmail.com> wrote:
>> >> In theory we should allow much more than that. The problem is just that we can't.
>> >>
>> >> We have the following issues:
>> >> 1. For swapping out stuff we need to make sure that we can allocate temporary pages.
>> >> Because of this TTM has a fixed 50% limit where it starts to unmap memory from GPUs.
>> >> So currently even with a higher GTT limit you can't actually use this.
>> >>
>> >> 2. Apart from the test case of allocating textures with increasing power of two until it fails we also have a bunch of extremely stupid applications.
>> >> E.g. stuff like looking at the amount of memory available and trying preallocate everything.
>> > I hear you but we also have an increasing number of games that don't
>> > even start with 3 GiB. At some point (which I'd speculate has already
>> > been reached, I've seen a number of complaints of games that ran on
>> > deck but not on desktop linux because on deck we set amdgpu.gttsize)
>> > we have more games broken due to the low limit than there would be
>> > apps broken due to a high limit.
>>
>> That's a really good argument, but the issue is that it is fixable. It's
>> just that nobody had time to look into all the issues.
>>
>> If started efforts to fix this years ago, but there was always something
>> more important going on.
>>
>> So we are left with the choice of breaking old applications or new
>> applications or getting somebody working on fixing this.
>>
>> Christian.
>>
>> >
>> >> I'm working on this for years, but there aren't easy solutions to those issues. Felix has opted out for adding a separate domain for KFD allocations, but sooner or later we need to find a solution which works for everybody.
>> >>
>> >> Christian.
>> >>
>> >> Am 20.05.22 um 11:14 schrieb Marek Olšák:
>> >>
>> >> Ignore the silly tests. We only need to make sure games work. The current minimum requirement for running modern games is 8GB of GPU memory. Soon it will be 12GB. APUs will need to support that.
>> >>
>> >> Marek
>> >>
>> >> On Fri., May 20, 2022, 03:52 Christian König, <ckoenig.leichtzumerken at gmail.com> wrote:
>> >>> Am 19.05.22 um 16:34 schrieb Alex Deucher:
>> >>>> The current somewhat strange logic is in place because certain
>> >>>> GL unit tests for large textures can cause problems with the
>> >>>> OOM killer since there is no way to link this memory to a
>> >>>> process. The problem is this limit is often too low for many
>> >>>> modern games on systems with more memory so limit the logic to
>> >>>> systems with less than 8GB of main memory. For systems with 8
>> >>>> or more GB of system memory, set the GTT size to 3/4 of system
>> >>>> memory.
>> >>> It's unfortunately not only the unit tests, but some games as well.
>> >>>
>> >>> 3/4 of total system memory sounds reasonable to be, but I'm 100% sure
>> >>> that this will break some tests.
>> >>>
>> >>> Christian.
>> >>>
>> >>>> Signed-off-by: Alex Deucher <alexander.deucher at amd.com>
>> >>>> ---
>> >>>> drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c | 25 ++++++++++++++++++++-----
>> >>>> 1 file changed, 20 insertions(+), 5 deletions(-)
>> >>>>
>> >>>> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c
>> >>>> index 4b9ee6e27f74..daa0babcf869 100644
>> >>>> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c
>> >>>> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c
>> >>>> @@ -1801,15 +1801,30 @@ int amdgpu_ttm_init(struct amdgpu_device *adev)
>> >>>> /* Compute GTT size, either bsaed on 3/4th the size of RAM size
>> >>>> * or whatever the user passed on module init */
>> >>>> if (amdgpu_gtt_size == -1) {
>> >>>> + const u64 eight_GB = 8192ULL * 1024 * 1024;
>> >>>> struct sysinfo si;
>> >>>> + u64 total_memory, default_gtt_size;
>> >>>>
>> >>>> si_meminfo(&si);
>> >>>> - gtt_size = min(max((AMDGPU_DEFAULT_GTT_SIZE_MB << 20),
>> >>>> - adev->gmc.mc_vram_size),
>> >>>> - ((uint64_t)si.totalram * si.mem_unit * 3/4));
>> >>>> - }
>> >>>> - else
>> >>>> + total_memory = (u64)si.totalram * si.mem_unit;
>> >>>> + default_gtt_size = total_memory * 3 / 4;
>> >>>> + /* This somewhat strange logic is in place because certain GL unit
>> >>>> + * tests for large textures can cause problems with the OOM killer
>> >>>> + * since there is no way to link this memory to a process.
>> >>>> + * The problem is this limit is often too low for many modern games
>> >>>> + * on systems with more memory so limit the logic to systems with
>> >>>> + * less than 8GB of main memory.
>> >>>> + */
>> >>>> + if (total_memory < eight_GB) {
>> >>>> + gtt_size = min(max((AMDGPU_DEFAULT_GTT_SIZE_MB << 20),
>> >>>> + adev->gmc.mc_vram_size),
>> >>>> + default_gtt_size);
>> >>>> + } else {
>> >>>> + gtt_size = default_gtt_size;
>> >>>> + }
>> >>>> + } else {
>> >>>> gtt_size = (uint64_t)amdgpu_gtt_size << 20;
>> >>>> + }
>> >>>>
>> >>>> /* Initialize GTT memory pool */
>> >>>> r = amdgpu_gtt_mgr_init(adev, gtt_size);
>>
>
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