On 2017å¹´05æ??12æ?¥ 16:43, Christian König wrote: > Am 12.05.2017 um 10:37 schrieb zhoucm1: >> >> >> On 2017å¹´05æ??12æ?¥ 16:33, Christian König wrote: >>> Am 12.05.2017 um 10:25 schrieb zhoucm1: >>>> >>>> On 2017å¹´05æ??10æ?¥ 05:47, Kasiviswanathan, Harish wrote: >>>>> Hi, >>>>> >>>>> Please review the patch set that supports amdgpu VM update via CPU. This feature provides improved performance for compute (HSA) where mapping / unmapping is carried out (by Kernel) independent of command submissions (done directly by user space). This version doesn't support shadow copy of VM page tables for CPU based update. >>>> I think your improved performance is from less waiting for cs, >>>> generally, SDMA engine updating page table is faster than CPU, >>>> otherwise we don't need sdma for updating PT. >>>> So whether your this improvement proves we have some redundant sync >>>> when mapping / unmapping, if yes, we should fix that, then not sure >>>> if CPU method is need or not. >>> >>> The problem is that the KFD is designed synchronously for page table >>> updates. In other words they need to wait for the update to finish >>> and that takes time. >>> >>> Apart from that your comment is absolutely correct, we found that >>> the SDMA is sometimes much faster to do the update than the CPU. >> If the sdma is faster, even they wait for finish, which time is >> shorter than CPU, isn't it? Of course, the precondition is sdma is >> exclusive. They can reserve a sdma for PT updating. > > No, if I understood Felix numbers correctly the setup and wait time > for SDMA is a bit (but not much) longer than doing it with the CPU. > > What would really help is to fix the KFD design and work with async > page tables updates there as well. OK, no problem, just curious. Regards, David Zhou > > Regards, > Christian. > >> >> Regards, >> David Zhou >>> >>> Regards, >>> Christian. >>> >>>> >>>> Regards, >>>> David Zhou >>>>> Best Regards, >>>>> Harish >>>>> >>>>> >>>>> >>>>> _______________________________________________ >>>>> 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 > > -------------- next part -------------- An HTML attachment was scrubbed... URL: <https://lists.freedesktop.org/archives/amd-gfx/attachments/20170512/5f48316a/attachment.html>
