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. > 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
