On Wed 28-11-18 14:18:43, osalvador@xxxxxxx wrote: > On 2018-11-28 14:08, Michal Hocko wrote: > > On Wed 28-11-18 13:51:42, osalvador@xxxxxxx wrote: > > > > yep. Or when we extend a zone/node via hotplug. > > > > > > > > > The only thing I am worried about is that by doing that, the system > > > > > will account spanned_pages incorrectly. > > > > > > > > As long as end_pfn - start_pfn matches then I do not see what would be > > > > incorrect. > > > > > > If by end_pfn - start_pfn you mean zone_end_pfn - zone_start_pfn, > > > then we would still need to change zone_start_pfn when removing > > > the first section, and adjust spanned_pages in case we remove the last > > > section, > > > would not we? > > > > Why? Again, how is removing the last/first section of the zone any > > different from any other section? > > Because removing last/first section changes the zone's boundary. > A zone that you removed the first section, will no longer start > at zone_start_pfn. > > A quick glance points that, for example, compact_zone() relies on > zone_start_pfn > to get where the zone starts. > Now, if you remove the first section and zone_start_pfn does not get > adjusted, you > will get a wrong start. > > Maybe that is fine, I am not sure. > Sorry for looping here, but it is being difficult for me to grasp it. OK, so let me try again. What is the difference for a pfn walker to start at an offline pfn start from any other offlined section withing a zone boundary? I believe there is none because the pfn walker needs to skip over offline pfns anyway whether they start at a zone boundary or not. -- Michal Hocko SUSE Labs
