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 2018å¹´02æ??08æ?¥ 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; >>> _______________________________________________ >>> amd-gfx mailing list >>> amd-gfx at lists.freedesktop.org >>> https://lists.freedesktop.org/mailman/listinfo/amd-gfx >> _______________________________________________ >> amd-gfx mailing list >> amd-gfx at lists.freedesktop.org >> https://lists.freedesktop.org/mailman/listinfo/amd-gfx > _______________________________________________ > amd-gfx mailing list > amd-gfx at lists.freedesktop.org > https://lists.freedesktop.org/mailman/listinfo/amd-gfx
