On Tue 14-03-17 12:05:59, YASUAKI ISHIMATSU wrote: > > > On 03/13/2017 05:19 AM, Michal Hocko wrote: > >On Fri 10-03-17 12:39:27, Yasuaki Ishimatsu wrote: > >>On 03/10/2017 08:58 AM, Michal Hocko wrote: [...] > >>># echo online_movable > /sys/devices/system/memory/memory34/state > >>># grep . /sys/devices/system/memory/memory3?/valid_zones > >>>/sys/devices/system/memory/memory32/valid_zones:Normal > >>>/sys/devices/system/memory/memory33/valid_zones:Normal Movable > >>>/sys/devices/system/memory/memory34/valid_zones:Movable Normal > >>> > >> > >>I think there is no strong reason which kernel has the restriction. > >>By setting the restrictions, it seems to have made management of > >>these zone structs simple. > > > >Could you be more specific please? How could this make management any > >easier when udev is basically racing with the physical hotplug and the > >result is basically undefined? > > > > When changing zone from NORMAL(N) to MOVALBE(M), we must resize both zones, > zone->zone_start_pfn and zone->spanned_pages. Currently there is the > restriction. > > So we just simply change: > zone(N)->spanned_pages -= nr_pages > zone(M)->zone_start_pfn -= nr_pages Yes I understand how this made the implementation simpler. I was questioning how this made user management any easier. Changing valid zones which races with the hotplug consumer (e.g. udev) sounds like a terrible idea to me. Anyway, it seems that the initial assumption/restriction that all pages have to start on the zone Normal is not really needed. I have a preliminary patch which removes that and associates newly added pages with a zone at the online time and it seems to be working reasonably well. I have to iron out some corners before I post it. -- Michal Hocko SUSE Labs -- To unsubscribe from this list: send the line "unsubscribe linux-api" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
