On Thu 16-03-17 12:04:48, Dan Williams wrote: > On Thu, Mar 16, 2017 at 10:48 AM, Michal Hocko <mhocko@xxxxxxxxxx> wrote: > > Hi, > > I didn't get to look through the patch series yet and I might not be > > able before LSF/MM. How urgent is this? I am primarily asking because > > the memory hotplug is really convoluted right now and putting more on > > top doesn't really sound like the thing we really want. I have tried to > > simplify the code [1] already but this is an early stage work so I do > > not want to impose any burden on you. So I am wondering whether this > > is something that needs to be merged very soon or it can wait for the > > rework and hopefully end up being much simpler in the end as well. > > > > What do you think? > > In general, I think it's better to add new features after > reworks/cleanup, but it's not clear to me (yet) that the problem you > are trying to solve makes this sub-section enabling for ZONE_DEVICE > any simpler. > > > [1] http://lkml.kernel.org/r/20170315091347.GA32626@xxxxxxxxxxxxxx > > ZONE_DEVICE pages are never "online". The patch says "Instead we do > page->zone association from move_pfn_range which is called from > online_pages." which means the new scheme currently doesn't comprehend > the sprinkled ZONE_DEVICE hacks in the memory hotplug code. I hope we can get rid of those... > However, that said, I might take a look at whether the hacks belong in > the auto-online code so that we can share the delayed zone > initialization, but still skip marking the memory online per the > expectations of ZONE_DEVICE. I think this should be trivial. AFAIU it should be sufficient to split my move_pfn_range into online_pfn_range which would do the MMOP_ONLINE* handling and the real move_pfn_range which would do the zone specific association. Your devm_memremap_pages would then call this move_pfn_range after arch_add_memory. Or am I overlooking something? I would still have to addapt your changes to remove hardcoded section aligned expectations but that shouldn't be a big problem I guess. I still haven't looked into those deeply to fully understand them. > I expect it would be confusing to have > memblock devices in sysfs for ranges that can't be marked online? Well, if their only valid_zone would be ZONE_DEVICE then I believe it shouldn't be confusing much. -- Michal Hocko SUSE Labs -- 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>
