On 2016å¹´07æ??26æ?¥ 17:05, Christian König wrote: > Am 26.07.2016 um 10:41 schrieb zhoucm1: >> >> >> On 2016å¹´07æ??26æ?¥ 16:27, Christian König wrote: >>> Am 26.07.2016 um 07:33 schrieb zhoucm1: >>>> >>>> >>>> On 2016å¹´07æ??26æ?¥ 10:40, zhoucm1 wrote: >>>>> 1. We add an optional "shadow" flag so that when a BO in VRAM is >>>>> allocated we also allocate a shadow BO in GART. >>>>> >>>>> 2. We have another "backup" flag that says on the next command >>>>> submission the BO is backed up from VRAM to GART before that >>>>> submission. >>>>> >>>>> 3. We set the shadow flag for VM PD/PT BOs and every time we >>>>> modify them set the backup flag so they get backed up on next CS. >>>>> >>>>> 4. We add an IOCTL to allow setting the backup flag from userspace >>>>> so that we can trigger another backup even after the first CS. >>>> When I'm trying it and thinking more, a general shadow BO indeed be >>>> a sense way, but backup flag seems not necessary, mainly two reasons: >>>> 1. we cannot make sure backup job is completed when gpu reset happens. >>> >>> Correct, but we can't guarantee that for VM updates either. >> Since we directly fill pte info to shadow BO, not copy from VRAM to >> GTT. Which ensures shadow BO content always is right, event these >> jobs don't complete when gpu reset, but after gpu reset, we can sync >> these jobs, and then copy GTT to VRAM. The similar case is also same >> for shader BOs. So we should directly fill the shadow BOs. > > I see what you mean. The PTE update and the shadow update must be one > operation for this to be always consistent. > > Alternatively you could flip the order and do the update on the shadow > first and then copy the result to the real one. > > BTW: We should make this an optional feature, cause it will certainly > use a lot of memory and computation resources. Make sense. Can we depend on whether lockup is enabled or not? Regards, David Zhou > > Regards, > Christian. > >> >> Regards, >> David Zhou >>> >>>> 2. backup flag is to copy the whole BO, which seems overhead. If we >>>> update shadow BO along with BO in real time, e.g. PD/PT, we could >>>> only update some ptes not the entire BO. >>> >>> How about using a begin/end range of which parts of the BO needs to >>> be backed up instead of a flag? >>> >>>> So can we assume shadow BO always needed to backup if shadow flag >>>> is set? >>> >>> For shader BOs clearly not a good idea because they are rarely >>> update and so backing them up every time would be a huge overhead. >>> >>> Regards, >>> Christian. >>> >>>> >>>> Regards, >>>> David Zhou >>> >>> >> >> _______________________________________________ >> amd-gfx mailing list >> amd-gfx at lists.freedesktop.org >> https://lists.freedesktop.org/mailman/listinfo/amd-gfx > >
