On 25/10/16 18:17, Balbir Singh wrote: > > > On 25/10/16 15:15, Aneesh Kumar K.V wrote: >> Dave Hansen <dave.hansen@xxxxxxxxx> writes: >> >>> On 10/23/2016 09:31 PM, Anshuman Khandual wrote: >>>> This change is part of the isolation requiring coherent device memory nodes >>>> implementation. >>>> >>>> Isolation seeking coherent device memory node requires allocation isolation >>>> from implicit memory allocations from user space. Towards that effect, the >>>> memory should not be used for generic HugeTLB page pool allocations. This >>>> modifies relevant functions to skip all coherent memory nodes present on >>>> the system during allocation, freeing and auditing for HugeTLB pages. >>> >>> This seems really fragile. You had to hit, what, 18 call sites? What >>> are the odds that this is going to stay working? >> >> >> I guess a better approach is to introduce new node_states entry such >> that we have one that excludes coherent device memory numa nodes. One >> possibility is to add N_SYSTEM_MEMORY and N_MEMORY. >> >> Current N_MEMORY becomes N_SYSTEM_MEMORY and N_MEMORY includes >> system and device/any other memory which is coherent. >> > > I thought of this as well, but I would rather see N_COHERENT_MEMORY > as a flag. The idea being that some device memory is a part of > N_MEMORY, but N_COHERENT_MEMORY gives it additional attributes > >> All the isolation can then be achieved based on the nodemask_t used for >> allocation. So for allocations we want to avoid from coherent device we >> use N_SYSTEM_MEMORY mask or a derivative of that and where we are ok to >> allocate from CDM with fallbacks we use N_MEMORY. >> > > I suspect its going to be easier to exclude N_COHERENT_MEMORY. > >> All nodes zonelist will have zones from the coherent device nodes but we >> will not end up allocating from coherent device node zone due to the >> node mask used. >> >> >> This will also make sure we end up allocating from the correct coherent >> device numa node in the presence of multiple of them based on the >> distance of the coherent device node from the current executing numa >> node. >> > > The idea is good overall, but I think its going to be good to document > the exclusions with the flags > FWIW,, some of this is present in 8/8 Balbir -- 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>