On 2014/7/25 10:39, Zhang Zhen wrote: > On 2014/7/25 1:59, Dave Hansen wrote: >> On 07/24/2014 12:41 AM, Zhang Zhen wrote: >>> Currently memory-hotplug has two limits: >>> 1. If the memory block is in ZONE_NORMAL, you can change it to >>> ZONE_MOVABLE, but this memory block must be adjacent to ZONE_MOVABLE. >>> 2. If the memory block is in ZONE_MOVABLE, you can change it to >>> ZONE_NORMAL, but this memory block must be adjacent to ZONE_NORMAL. >>> >>> Without this patch, we don't know which zone a memory block is in. >>> So we don't know which memory block is adjacent to ZONE_MOVABLE or >>> ZONE_NORMAL. >>> >>> On the other hand, with this patch, we can easy to know newly added >>> memory is added as ZONE_NORMAL (for powerpc, ZONE_DMA, for x86_32, >>> ZONE_HIGHMEM). >> >> A section can contain more than one zone. This interface will lie about >> such sections, which is quite unfortunate. Hi Dave, You are right, i only considered the memory block added after machine booted. For a x86_64 machine booted with "mem=400M" and with 2GiB memory installed. Sample output of the sysfs files: # cat block_size_bytes 8000000 # cat memory0/zone_index DMA Here memory0 cantain DMA_ZONE and DMA32_ZONE. >> > 1. In arch_add_memory(), x86_64 add the new pages of the new memory block default to > ZONE_NORMAL (for powerpc, ZONE_DMA, for x86_32, ZONE_HIGHMEM). > > 2. In __offline_pages(), test_pages_in_a_zone() guaranteed the pages of a memory block > we try to offline are in the same zone. If a section contains more than one zone, > the memory block can not be offlined. > > Based on the above two points, i think the pages of a memory block are in one zone, and the sections > of a memory block are in one zone. > > Could you please explain in detail what is the case a section can contain more than one zone ? > > Thanks for your comments! > >> I'd really much rather see an interface that has a section itself >> enumerate to which zones it may be changed. The way you have it now, >> any user has to know the rules that you've laid out above. If the >> kernel changed those restrictions, we'd have to teach every application >> about the change in restrictions. >> Here you are right too, we should add an interface to show which zones a memory block may be changed to. So user doesn't need to know the rules above. I will send a new version. Thank you very much ! > > This interface is designed to show which zone a memory block is in. If the kernel changed those > restrictions, this interface doesn't need to change. > For a x86_64 machine booted with "mem=400M" and with 2GiB memory installed. > Sample output of the sysfs files: > # cat block_size_bytes > 8000000 > # cat memory0/zone_index > DMA > # cat memory1/zone_index > DMA32 > # cat memory2/zone_index > DMA32 > # cat memory3/zone_index > DMA32 > # echo 0x20000000 > probe > # cat memory4/zone_index > Normal > # echo online > memory4/state > # cat memory4/zone_index > Normal > > # echo offline > memory4/state > # echo online_movable > memory4/state > # cat memory4/zone_index > Movable > > Thanks! > > Best regards! >> >> >> >> . >> > > > -- > 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> > > -- 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>