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 Balbir Singh. -- 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>