GTT memory usage overflow

GTT memory usage overflow

[sunnanyong]

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Hi All,
     When the gtt memory is used up, application continues to use gtt , then the gtt will overflow,
the gtt available will be negative(cat /sys/kernel/debug/dri/1/amdgpu_gtt_mm), and more system memory is used as GTT, is it normal?
My kernel  is newest v4.18 master,  I add "cma=0 amdgpu.gttsize=24576" in kernel boot cmdline.

Please help, Thanks : )

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Re: GTT memory usage overflow

[Christian König]

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Hi,

no that is certainly not normal.

We temporary allow the kernel to allocate more pages than available when 
we bind stuff into the GART, but that shouldn't have this effect.

How do you allocate the GTT space?

Regards,
Christian.

Am 12.07.2018 um 17:50 schrieb sunnanyong:
>
> Hi All,
>
> When the gtt memory is used up, application continues to use gtt , 
> then the gtt will overflow,
>
> the gtt available will be negative(cat 
> /sys/kernel/debug/dri/1/amdgpu_gtt_mm), and more system memory is used 
> as GTT, is it normal?
>
> My kernel  is newest v4.18 master,  I add “cma=0 amdgpu.gttsize=24576” 
> in kernel boot cmdline.
>
> Please help, Thanks : )
>
>
>
> _______________________________________________
> amd-gfx mailing list
> amd-gfx-PD4FTy7X32lNgt0PjOBp9y5qC8QIuHrW@public.gmane.org
> https://lists.freedesktop.org/mailman/listinfo/amd-gfx


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Re: GTT memory usage overflow

[Michel Dänzer]

On 2018-07-13 09:00 AM, Christian König wrote:
> Hi,
> 
> no that is certainly not normal.
> 
> We temporary allow the kernel to allocate more pages than available when
> we bind stuff into the GART, but that shouldn't have this effect.

mgr->available can happen to be negative when amdgpu_gtt_mgr_debug is
called, can't it? I.e. we should clamp it to 0 there as well, same as in
amdgpu_gtt_mgr_usage (or maybe just use that for both values in
amdgpu_gtt_mgr_debug).


-- 
Earthling Michel Dänzer               |               http://www.amd.com
Libre software enthusiast             |             Mesa and X developer
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Re: GTT memory usage overflow

[Christian König]

Am 13.07.2018 um 09:40 schrieb Michel Dänzer:
> On 2018-07-13 09:00 AM, Christian König wrote:
>> Hi,
>>
>> no that is certainly not normal.
>>
>> We temporary allow the kernel to allocate more pages than available when
>> we bind stuff into the GART, but that shouldn't have this effect.
> mgr->available can happen to be negative when amdgpu_gtt_mgr_debug is
> called, can't it? I.e. we should clamp it to 0 there as well, same as in
> amdgpu_gtt_mgr_usage (or maybe just use that for both values in
> amdgpu_gtt_mgr_debug).

Yeah, but that happens only temporary while binding things into GART.

You must be really really lucky if you can see that in debugfs and from 
the description it sounds more like the reporter sees negative values 
all the time.

I really wonder how that could happen.

Christian.
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