On Thu 10-09-20 22:31:09, David Hildenbrand wrote: > > > > Am 10.09.2020 um 22:01 schrieb Dave Hansen <dave.hansen@xxxxxxxxx>: > > > > On 9/10/20 3:20 AM, David Hildenbrand wrote: > >> I was just exploring how /sys/devices/system/memory/memoryX/phys_device > >> is/was used. It's one of these interfaces that most probably never > >> should have been added but now we are stuck with it. > > > > While I'm all for cleanups, what specific problems is phys_device causing? > > > > Mostly stumbling over it, understanding that it is basically unused > with new userspace for good reason, questioning its existence. > > E.g., I am working on virtio-mem support for s390x. Displaying > misleading/wrong phys_device indications isn‘t particularly helpful > - especially once there are different ways to hotplug memory for an > architecture. > > > Are you hoping that we can just remove users of memoryX/* until there > > are no more left, and this is the easiest place to start? > > At least reducing it to a minimum with clear semantics. Even with > automatic onlining there are still reasons why we need to keep the > interface for now (e.g., reloading kexec to update the kdump headers > on memory hot(un)plug). But also standby memory handling on s399x > requires it (->manual onlining). While I agree that the existing interface is far from ideal, I am not sure it makes much sense to invest energy into cleaning it up. We can have a pig with a lipstick but but this will not solve the underlying problem that we have I believe. The interface doesn't scale with the block count (especially on some platforms like ppc), it is too inflexible (single size of the block) and many others. I believe we need a completely new interface which would effectively deprecate the existing one. One could still chose to use the old interface but new usecases would use the new one ideally. I have brought that up earlier already without much follow up (http://lkml.kernel.org/r/20200619120704.GD12177@xxxxxxxxxxxxxx) -- Michal Hocko SUSE Labs
