[PATCH 3/9] drm/amdgpu: add amdgpu module parameter for zfb
Christian König
christian.koenig at amd.com
Thu Feb 8 09:05:14 UTC 2018
Well ZFB is only for emulation, so the risk should be minimal.
According to my test CMA works fine and I think it is a must have for
upstreaming ZFB.
Regards,
Christian.
Am 08.02.2018 um 09:40 schrieb He, Roger:
> For the CMA, I have some concern.
> First, it is strongly depend on other module's robustness which can use CMA memory with flag __GFP_MOVABLE.
> My mean is dma_alloc_coherent sometimes will fail because its owner cannot migrate its memory out from CMA range because some internal bugs.
> Second because memory migration, the CMA memory allocation performance is not very good as normal.
> When I used CMA feature with 3.16 kernel encountered more issues.
>
> So not pretty sure CMA module and other modules are very robust in 4.15 kernel.
>
> Thanks
> Roger(Hongbo.He)
>
> -----Original Message-----
> From: amd-gfx [mailto:amd-gfx-bounces at lists.freedesktop.org] On Behalf Of Christian K?nig
> Sent: Thursday, February 08, 2018 4:10 PM
> To: Zhang, Hawking <Hawking.Zhang at amd.com>; Zhou, David(ChunMing) <David1.Zhou at amd.com>; Xu, Feifei <Feifei.Xu at amd.com>; amd-gfx at lists.freedesktop.org
> Subject: Re: [PATCH 3/9] drm/amdgpu: add amdgpu module parameter for zfb
>
> Am 08.02.2018 um 05:51 schrieb Zhang, Hawking:
>> Apart from the allocation failure, reserving 1024M cma is also not realistic....
> Sure it is, I just tried it and it works perfectly fine. The option even accepts a G postfix for gigabytes, e.g. I can specify cma=8G on my 32GB Ryzen box and get exactly 8GB CMA space reserved.
>
> Regarding the allocation failure using the DMA path there was a thread quite some time ago. IIRC the argument was that TTM only allocates a single page at a time and so should never run into any CMA allocator and according to my tests at least with IOMMU enabled that seems to be fixed now.
>
> The key point is that CMA was specially crafted to avoid all those mem= workarounds and I think this is now a must have. See here https://de.slideshare.net/kerneltlv/continguous-memory-allocator-in-the-linux-kernel
> as well.
>
> Regards,
> Christian.
>
>> Regards,
>> Hawking
>>
>> -----Original Message-----
>> From: amd-gfx [mailto:amd-gfx-bounces at lists.freedesktop.org] On Behalf
>> Of Chunming Zhou
>> Sent: Thursday, February 08, 2018 12:35
>> To: Koenig, Christian <Christian.Koenig at amd.com>; Xu, Feifei
>> <Feifei.Xu at amd.com>; amd-gfx at lists.freedesktop.org
>> Subject: Re: [PATCH 3/9] drm/amdgpu: add amdgpu module parameter for
>> zfb
>>
>>
>>
>> On 2018年02月08日 02:48, Christian König wrote:
>>> Hi Feifei,
>>>
>>> ok the correct approach of doing this:
>>> 1. Compile the kernel with CONFIG_DMA_CMA.
>>> 2. Specify cma=1025M on the kernel command line.
>>> 3. Call dma_alloc_coherent() to allocate up to 1GB of memory for ZFB.
>> Have you tried CMA? In early time, I tried it. If CMA is enabled, then ttm dma pool allocation will use cma, and when cma is used up, then ttm dma pool allocation will fail.
>> Not sure if the issue is fixed now.
>>
>> Regards,
>> David Zhou
>>> Couldn't figure out of hand what alignment is necessary here, but
>>> that should just be a typing exercise.
>>>
>>> Regards,
>>> Christian.
>>>
>>> Am 07.02.2018 um 14:18 schrieb Christian König:
>>>> Hi Feifei,
>>>>
>>>> mhm, so you're approach is to limit the memory the Linux kernel grab
>>>> using the mem= parameter and then give that memory to amdgpu, correct?
>>>>
>>>> If that's the case then this is most likely a NAK. Cause this sounds
>>>> like a perfect example for the CMA.
>>>>
>>>> Never worked with that subsystem before, but in theory you should be
>>>> able to give the cma=1G parameter to the kernel and by doing so you
>>>> reserve 1GB of contiguous memory for use by device drivers.
>>>>
>>>> Going to dig a bit deeper into that and trying to find to
>>>> documentation about it, Christian.
>>>>
>>>> Am 07.02.2018 um 13:34 schrieb Feifei Xu:
>>>>> Users can pass in an array to decide enable/disable Zero Frame Buffer.
>>>>> zfb[0] = zfb_size(MB), zfb[1] = zfb_phys_addr(MB).
>>>>> If zbf_size > 0, zfb is enabled. Otherwise disabled.
>>>>> Usage for example:
>>>>> modprobe amdgpu zfb={256,4096}
>>>>>
>>>>> Change-Id: I340fcb36b5655f24551056e685b74559d7599680
>>>>> Signed-off-by: Feifei Xu <Feifei.Xu at amd.com>
>>>>> ---
>>>>> drivers/gpu/drm/amd/amdgpu/amdgpu.h | 1 +
>>>>> drivers/gpu/drm/amd/amdgpu/amdgpu_drv.c | 5 +++++
>>>>> 2 files changed, 6 insertions(+)
>>>>>
>>>>> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu.h
>>>>> b/drivers/gpu/drm/amd/amdgpu/amdgpu.h
>>>>> index 1b4c5ad..be79cb1 100644
>>>>> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu.h
>>>>> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu.h
>>>>> @@ -129,6 +129,7 @@ extern int amdgpu_job_hang_limit;
>>>>> extern int amdgpu_lbpw;
>>>>> extern int amdgpu_compute_multipipe;
>>>>> extern int amdgpu_gpu_recovery;
>>>>> +extern ulong amdgpu_zfb[];
>>>>> #ifdef CONFIG_DRM_AMDGPU_SI
>>>>> extern int amdgpu_si_support;
>>>>> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_drv.c
>>>>> b/drivers/gpu/drm/amd/amdgpu/amdgpu_drv.c
>>>>> index 3897179..af84815 100644
>>>>> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_drv.c
>>>>> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_drv.c
>>>>> @@ -132,6 +132,7 @@ int amdgpu_job_hang_limit = 0;
>>>>> int amdgpu_lbpw = -1;
>>>>> int amdgpu_compute_multipipe = -1;
>>>>> int amdgpu_gpu_recovery = -1; /* auto */
>>>>> +ulong amdgpu_zfb[2] = {0,4096UL}; /* {0,0x100000000} */
>>>>> MODULE_PARM_DESC(vramlimit, "Restrict VRAM for testing, in
>>>>> megabytes");
>>>>> module_param_named(vramlimit, amdgpu_vram_limit, int, 0600); @@
>>>>> -290,6 +291,10 @@ module_param_named(compute_multipipe,
>>>>> amdgpu_compute_multipipe, int, 0444);
>>>>> MODULE_PARM_DESC(gpu_recovery, "Enable GPU recovery mechanism,
>>>>> (1 = enable, 0 = disable, -1 = auto");
>>>>> module_param_named(gpu_recovery, amdgpu_gpu_recovery, int,
>>>>> 0444);
>>>>> +MODULE_PARM_DESC(zfb,
>>>>> + "Enable Zero Frame Buffer feature (zfb will be set like
>>>>> xxxx,xxxx(zfb_size MB,zfb_phys_addr MB),default disabled)");
>>>>> +module_param_array_named(zfb, amdgpu_zfb, ulong, NULL, 0444);
>>>>> +
>>>>> #ifdef CONFIG_DRM_AMDGPU_SI
>>>>> int amdgpu_si_support = 1;
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