On Tue, Nov 14, 2023 at 10:43:13AM +0100, Michal Hocko wrote: > On Fri 10-11-23 22:42:39, Gregory Price wrote: > [...] > > If I can ask, do you think it would be out of line to propose a major > > refactor to mempolicy to enable external task's the ability to change a > > running task's mempolicy *as well as* a cgroup-wide mempolicy component? > > No, I actually think this is a reasonable idea. pidfd_setmempolicy is a > generally useful extension. The mempolicy code is heavily current task > based and there might be some challenges but I believe this will a) > improve the code base and b) allow more usecases. Just read up on the pidfd_set_mempolicy lore, and yes I'm seeing all the same problems (I know there was discussion of vma policies, but i think that can be a topic for later). Have some thoughts on this, but will take some time to work through a few refactoring tickets first. > > That being said, I still believe that a cgroup based interface is a much > better choice over a global one. Cpusets seem to be a good fit as the > controller does control memory placement wrt NUMA interfaces. I think cpusets is a non-starter due to the global spinlock required when reading informaiton from it: https://elixir.bootlin.com/linux/latest/source/kernel/cgroup/cpuset.c#L391 Unless the proposal is to place the weights as a global cgroups value, in which case I think it would be better placed in default_mempolicy :]
