On Sat, Sep 30, 2017 at 10:57:38AM +0800, Bob Liu wrote: > On 2017/9/27 0:16, Jerome Glisse wrote: > > On Tue, Sep 26, 2017 at 05:56:26PM +0800, Bob Liu wrote: > >> On Tue, Sep 12, 2017 at 7:36 AM, Jerome Glisse <jglisse@xxxxxxxxxx> wrote: > >>> On Sun, Sep 10, 2017 at 07:22:58AM +0800, Bob Liu wrote: > >>>> On Wed, Sep 6, 2017 at 3:36 AM, Jerome Glisse <jglisse@xxxxxxxxxx> wrote: > >>>>> On Thu, Jul 20, 2017 at 08:48:20PM -0700, Dan Williams wrote: > >>>>>> On Thu, Jul 20, 2017 at 6:41 PM, Jerome Glisse <jglisse@xxxxxxxxxx> wrote: > [...] > >>>>> So i pushed a branch with WIP for nouveau to use HMM: > >>>>> > >>>>> https://cgit.freedesktop.org/~glisse/linux/log/?h=hmm-nouveau > >>>>> > >>>> > >>>> Nice to see that. > >>>> Btw, do you have any plan for a CDM-HMM driver? CPU can write to > >>>> Device memory directly without extra copy. > >>> > >>> Yes nouveau CDM support on PPC (which is the only CDM platform commercialy > >>> available today) is on the TODO list. Note that the driver changes for CDM > >>> are minimal (probably less than 100 lines of code). From the driver point > >>> of view this is memory and it doesn't matter if it is CDM or not. > >>> > >> > >> It seems have to migrate/copy memory between system-memory and > >> device-memory even in HMM-CDM solution. > >> Because device-memory is not added into buddy system, the page fault > >> for normal malloc() always allocate memory from system-memory!! > >> If the device then access the same virtual address, the data is copied > >> to device-memory. > >> > >> Correct me if I misunderstand something. > >> @Balbir, how do you plan to make zero-copy work if using HMM-CDM? > > > > Device can access system memory so copy to device is _not_ mandatory. Copying > > data to device is for performance only ie the device driver take hint from > > userspace and monitor device activity to decide which memory should be migrated > > to device memory to maximize performance. > > > > Moreover in some previous version of the HMM patchset we had an helper that > > Could you point in which version? I'd like to have a look. I will need to dig in. > > > allowed to directly allocate device memory on device page fault. I intend to > > post this helper again. With that helper you can have zero copy when device > > is the first to access the memory. > > > > Plan is to get what we have today work properly with the open source driver > > and make it perform well. Once we get some experience with real workload we > > might look into allowing CPU page fault to be directed to device memory but > > at this time i don't think we need this. > > > > For us, we need this feature that CPU page fault can be direct to device memory. > So that don't need to copy data from system memory to device memory. > Do you have any suggestion on the implementation? I'll try to make a prototype patch. Why do you need that ? What is the device and what are the requirement ? Jérôme -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>
