On Wed, May 24, 2017 at 10:39:57AM +0200, Michal Hocko wrote: > On Wed 24-05-17 10:20:22, Heiko Carstens wrote: > > Having the ZONE_MOVABLE default was actually the only point why s390's > > arch_add_memory() was rather complex compared to other architectures. > > > > We always had this behaviour, since we always wanted to be able to offline > > memory after it was brought online. Given that back then "online_movable" > > did not exist, the initial s390 memory hotplug support simply added all > > additional memory to ZONE_MOVABLE. > > > > Keeping the default the same would be quite important. > > Hmm, that is really unfortunate because I would _really_ like to get rid > of the previous semantic which was really awkward. The whole point of > the rework is to get rid of the nasty zone shifting. > > Is it an option to use `online_movable' rather than `online' in your setup? > Btw. my long term plan is to remove the zone range constrains altogether > so you could online each memblock to the type you want. Would that be > sufficient for you in general? Why is it a problem to change the default for 'online'? As far as I can see that doesn't have too much to do with the order of zones, no? By the way: we played around a bit with the changes wrt memory hotplug. There are a two odd things: 1) With the new code I can generate overlapping zones for ZONE_DMA and ZONE_NORMAL: --- new code: DMA [mem 0x0000000000000000-0x000000007fffffff] Normal [mem 0x0000000080000000-0x000000017fffffff] # cat /sys/devices/system/memory/block_size_bytes 10000000 # cat /sys/devices/system/memory/memory5/valid_zones DMA # echo 0 > /sys/devices/system/memory/memory5/online # cat /sys/devices/system/memory/memory5/valid_zones Normal # echo 1 > /sys/devices/system/memory/memory5/online Normal # cat /proc/zoneinfo Node 0, zone DMA spanned 524288 <----- present 458752 managed 455078 start_pfn: 0 <----- Node 0, zone Normal spanned 720896 present 589824 managed 571648 start_pfn: 327680 <----- So ZONE_DMA ends within ZONE_NORMAL. This shouldn't be possible, unless this restriction is gone? --- old code: # echo 0 > /sys/devices/system/memory/memory5/online # cat /sys/devices/system/memory/memory5/valid_zones DMA # echo online_movable > /sys/devices/system/memory/memory5/state -bash: echo: write error: Invalid argument # echo online_kernel > /sys/devices/system/memory/memory5/state -bash: echo: write error: Invalid argument # echo online > /sys/devices/system/memory/memory5/state # cat /sys/devices/system/memory/memory5/valid_zones DMA 2) Another oddity is that after a memory block was brought online it's association to ZONE_NORMAL or ZONE_MOVABLE seems to be fixed. Even if it is brought offline afterwards: # cat /sys/devices/system/memory/memory16/valid_zones Normal Movable # echo online_movable > /sys/devices/system/memory/memory16/state # echo offline > /sys/devices/system/memory/memory16/state # cat /sys/devices/system/memory/memory16/valid_zones Movable <---- should be "Normal Movable" I assume this happens because start_pfn and spanned pages of the zones aren't updated if a memory block at the beginning or end of a zone is brought offline. -- 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>
