On 10/11/2017 10:49 AM, Michael Ellerman wrote: > Michael Ellerman <mpe@xxxxxxxxxxxxxx> writes: >> Michal Hocko <mhocko@xxxxxxxxxx> writes: >>> On Tue 10-10-17 23:05:08, Michael Ellerman wrote: >>>> Michal Hocko <mhocko@xxxxxxxxxx> writes: >>>>> From: Michal Hocko <mhocko@xxxxxxxx> >>>>> Memory offlining can fail just too eagerly under a heavy memory pressure. >>>>> >>>>> [ 5410.336792] page:ffffea22a646bd00 count:255 mapcount:252 mapping:ffff88ff926c9f38 index:0x3 >>>>> [ 5410.336809] flags: 0x9855fe40010048(uptodate|active|mappedtodisk) >>>>> [ 5410.336811] page dumped because: isolation failed >>>>> [ 5410.336813] page->mem_cgroup:ffff8801cd662000 >>>>> [ 5420.655030] memory offlining [mem 0x18b580000000-0x18b5ffffffff] failed >>>>> >>>>> Isolation has failed here because the page is not on LRU. Most probably >>>>> because it was on the pcp LRU cache or it has been removed from the LRU >>>>> already but it hasn't been freed yet. In both cases the page doesn't look >>>>> non-migrable so retrying more makes sense. >>>> This breaks offline for me. >>>> >>>> Prior to this commit: >>>> /sys/devices/system/memory/memory0# time echo 0 > online >>>> -bash: echo: write error: Device or resource busy >>>> >>>> real 0m0.001s >>>> user 0m0.000s >>>> sys 0m0.001s >>>> >>>> After: >>>> /sys/devices/system/memory/memory0# time echo 0 > online >>>> -bash: echo: write error: Device or resource busy >>>> >>>> real 2m0.009s >>>> user 0m0.000s >>>> sys 1m25.035s >>>> >>>> There's no way that block can be removed, it contains the kernel text, >>>> so it should instantly fail - which it used to. >>> OK, that means that start_isolate_page_range should have failed but it >>> hasn't for some reason. I strongly suspect has_unmovable_pages is doing >>> something wrong. Is the kernel text marked somehow? E.g. PageReserved? >> I'm not sure how the text is marked, will have to dig into that. > Yeah it's reserved: > > $ grep __init_begin /proc/kallsyms > c000000000d70000 T __init_begin > $ ./page-types -r -a 0x0,0xd7 > flags page-count MB symbolic-flags long-symbolic-flags > 0x0000000100000000 215 13 __________________________r_______________ reserved > total 215 13 Hey Michael, What tool is this 'page-types' ? -- 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>
