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: > > On Fri, Jul 21, 2017 at 09:15:29AM +0800, Bob Liu wrote: > >> On 2017/7/20 23:03, Jerome Glisse wrote: > >> > On Wed, Jul 19, 2017 at 05:09:04PM +0800, Bob Liu wrote: > >> >> On 2017/7/19 10:25, Jerome Glisse wrote: > >> >>> On Wed, Jul 19, 2017 at 09:46:10AM +0800, Bob Liu wrote: > >> >>>> On 2017/7/18 23:38, Jerome Glisse wrote: > >> >>>>> On Tue, Jul 18, 2017 at 11:26:51AM +0800, Bob Liu wrote: > >> >>>>>> On 2017/7/14 5:15, Jérôme Glisse wrote: > > > > [...] > > > >> >> Then it's more like replace the numa node solution(CDM) with ZONE_DEVICE > >> >> (type MEMORY_DEVICE_PUBLIC). But the problem is the same, e.g how to make > >> >> sure the device memory say HBM won't be occupied by normal CPU allocation. > >> >> Things will be more complex if there are multi GPU connected by nvlink > >> >> (also cache coherent) in a system, each GPU has their own HBM. > >> >> > >> >> How to decide allocate physical memory from local HBM/DDR or remote HBM/ > >> >> DDR? > >> >> > >> >> If using numa(CDM) approach there are NUMA mempolicy and autonuma mechanism > >> >> at least. > >> > > >> > NUMA is not as easy as you think. First like i said we want the device > >> > memory to be isolated from most existing mm mechanism. Because memory > >> > is unreliable and also because device might need to be able to evict > >> > memory to make contiguous physical memory allocation for graphics. > >> > > >> > >> Right, but we need isolation any way. > >> For hmm-cdm, the isolation is not adding device memory to lru list, and many > >> if (is_device_public_page(page)) ... > >> > >> But how to evict device memory? > > > > What you mean by evict ? Device driver can evict whenever they see the need > > to do so. CPU page fault will evict too. Process exit or munmap() will free > > the device memory. > > > > Are you refering to evict in the sense of memory reclaim under pressure ? > > > > So the way it flows for memory pressure is that if device driver want to > > make room it can evict stuff to system memory and if there is not enough > > system memory than thing get reclaim as usual before device driver can > > make progress on device memory reclaim. > > > > > >> > Second device driver are not integrated that closely within mm and the > >> > scheduler kernel code to allow to efficiently plug in device access > >> > notification to page (ie to update struct page so that numa worker > >> > thread can migrate memory base on accurate informations). > >> > > >> > Third it can be hard to decide who win between CPU and device access > >> > when it comes to updating thing like last CPU id. > >> > > >> > Fourth there is no such thing like device id ie equivalent of CPU id. > >> > If we were to add something the CPU id field in flags of struct page > >> > would not be big enough so this can have repercusion on struct page > >> > size. This is not an easy sell. > >> > > >> > They are other issues i can't think of right now. I think for now it > >> > >> My opinion is most of the issues are the same no matter use CDM or HMM-CDM. > >> I just care about a more complete solution no matter CDM,HMM-CDM or other ways. > >> HMM or HMM-CDM depends on device driver, but haven't see a public/full driver to > >> demonstrate the whole solution works fine. > > > > I am working with NVidia close source driver team to make sure that it works > > well for them. I am also working on nouveau open source driver for same NVidia > > hardware thought it will be of less use as what is missing there is a solid > > open source userspace to leverage this. Nonetheless open source driver are in > > the work. > > Can you point to the nouveau patches? I still find these HMM patches > un-reviewable without an upstream consumer. I am still working on those, i hope i will be able to post them in 3 weeks or so. Cheers, 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>
