On Mon, Mar 19, 2018 at 3:27 PM, Christian König <christian.koenig at amd.com> wrote: > I think that the consensus with Alex and me is that we should avoid > exactly that. > > Overriding the preferred domain in the kernel is a no-go for that patch > set, so please implement the discussed changes in Mesa. > I don't see how Mesa can make a smarter decision than the kernel. If you overwrite the preferred domain of the buffer in the kernel, there will be no ping-ponging between domains. Mesa never changes the initial preferred domain. Marek > > Regards, > Christian. > > > Am 19.03.2018 um 20:22 schrieb Li, Samuel: > >> I agree with Marek/Michel: since kernel sets the domain before scanning >> out, it shall update the preferred domain here too. >> >> Regards, >> Samuel Li >> >> >> -----Original Message----- >>> From: Koenig, Christian >>> Sent: Thursday, March 08, 2018 4:07 AM >>> To: Michel Dänzer <michel at daenzer.net>; Li, Samuel >>> <Samuel.Li at amd.com>; Alex Deucher <alexdeucher at gmail.com> >>> Cc: amd-gfx list <amd-gfx at lists.freedesktop.org> >>> Subject: Re: [PATCH 1/2] drm/amdgpu: Enable scatter gather display >>> support >>> >>> Am 08.03.2018 um 09:35 schrieb Michel Dänzer: >>> >>>> On 2018-03-07 10:47 AM, Christian König wrote: >>>> >>>>> Am 07.03.2018 um 09:42 schrieb Michel Dänzer: >>>>> >>>>>> On 2018-03-06 07:23 PM, Christian König wrote: >>>>>> >>>>>> E.g. the last time I tested it placing things into GTT still >>>>>>> resulted in quite a performance penalty for rendering. >>>>>>> >>>>>> FWIW, I think the penalty is most likely IOMMU related. Last time I >>>>>> tested, I couldn't measure a big difference with IOMMU disabled. >>>>>> >>>>> No, the penalty I'm talking about came from the ping/pong we did with >>>>> the scanout buffers. >>>>> >>>>> See when I tested this the DDX and Mesa where unmodified, so both >>>>> still assumed VRAM as placement for scanout BOs, but the kernel >>>>> forced scanout BOs into GTT for testing. >>>>> >>>>> So what happened was that on scanout we moved the VRAM BO to GTT >>>>> >>>> and >>> >>>> after unpinning it on the first command submission which used the BO >>>>> we moved it back to VRAM again. >>>>> >>>> In the meantime, I've had the same idea as Marek: Can't the kernel >>>> driver simply change the BO's preferred domain to GTT when scanning >>>> out from it? Then it won't move back to VRAM. >>>> >>> Yes, I've considered this as well. >>> >>> But I think making the decision in Mesa is the cleaner approach. >>> >>> E.g. so far we only override the placement decision of userspace for two >>> reasons: >>> 1. We where running out of memory in VRAM. >>> 2. We have a hardware restriction which makes VRAM usage mandatory. >>> >>> And even then we never adjust the placement permanently, we just >>> temporary moved the buffer where it was needed and moved it back after >>> the operation completed. >>> >>> Additional to that Mesa might want to set even more flags and/or changes >>> it's behavior. E.g. use a tilling mode which both importer and export in >>> an >>> A+A laptop understands etc... >>> >>> Regards, >>> Christian. >>> >> > _______________________________________________ > amd-gfx mailing list > amd-gfx at lists.freedesktop.org > https://lists.freedesktop.org/mailman/listinfo/amd-gfx > -------------- next part -------------- An HTML attachment was scrubbed... URL: <https://lists.freedesktop.org/archives/amd-gfx/attachments/20180319/56740ea9/attachment.html>
