On Tue, Aug 04, 2020 at 01:16:45AM +0000, HORIGUCHI NAOYA(堀口 直也) wrote: > On Mon, Aug 03, 2020 at 03:07:09PM -0400, Qian Cai wrote: > > On Fri, Jul 31, 2020 at 12:20:56PM +0000, nao.horiguchi@xxxxxxxxx wrote: > > > This patchset is the latest version of soft offline rework patchset > > > targetted for v5.9. > > > > > > Main focus of this series is to stabilize soft offline. Historically soft > > > offlined pages have suffered from racy conditions because PageHWPoison is > > > used to a little too aggressively, which (directly or indirectly) invades > > > other mm code which cares little about hwpoison. This results in unexpected > > > behavior or kernel panic, which is very far from soft offline's "do not > > > disturb userspace or other kernel component" policy. > > > > > > Main point of this change set is to contain target page "via buddy allocator", > > > where we first free the target page as we do for normal pages, and remove > > > from buddy only when we confirm that it reaches free list. There is surely > > > race window of page allocation, but that's fine because someone really want > > > that page and the page is still working, so soft offline can happily give up. > > > > > > v4 from Oscar tries to handle the race around reallocation, but that part > > > seems still work in progress, so I decide to separate it for changes into > > > v5.9. Thank you for your contribution, Oscar. > > > > > > The issue reported by Qian Cai is fixed by patch 16/16. > > > > > > This patchset is based on v5.8-rc7-mmotm-2020-07-27-18-18, but I applied > > > this series after reverting previous version. > > > Maybe https://github.com/Naoya-Horiguchi/linux/commits/soft-offline-rework.v5 > > > shows what I did more precisely. > > > > > > Any other comment/suggestion/help would be appreciated. > > > > There is another issue with this patchset (with and without the patch [1]). > > > > [1] https://lore.kernel.org/lkml/20200803133657.GA13307@xxxxxxxxxxxxxxxxxxxxxxxxxxx/ > > > > Arm64 using 512M-size hugepages starts to fail allocations prematurely. > > > > # ./random 1 > > - start: migrate_huge_offline > > - use NUMA nodes 0,1. > > - mmap and free 2147483648 bytes hugepages on node 0 > > - mmap and free 2147483648 bytes hugepages on node 1 > > madvise: Cannot allocate memory > > > > [ 284.388061][ T3706] soft offline: 0x956000: hugepage isolation failed: 0, page count 2, type 17ffff80001000e (referenced|uptodate|dirty|head) > > [ 284.400777][ T3706] Soft offlining pfn 0x8e000 at process virtual address 0xffff80000000 > > [ 284.893412][ T3706] Soft offlining pfn 0x8a000 at process virtual address 0xffff60000000 > > [ 284.901539][ T3706] soft offline: 0x8a000: hugepage isolation failed: 0, page count 2, type 7ffff80001000e (referenced|uptodate|dirty|head) > > [ 284.914129][ T3706] Soft offlining pfn 0x8c000 at process virtual address 0xffff80000000 > > [ 285.433497][ T3706] Soft offlining pfn 0x88000 at process virtual address 0xffff60000000 > > [ 285.720377][ T3706] Soft offlining pfn 0x8a000 at process virtual address 0xffff80000000 > > [ 286.281620][ T3706] Soft offlining pfn 0xa000 at process virtual address 0xffff60000000 > > [ 286.290065][ T3706] soft offline: 0xa000: hugepage migration failed -12, type 7ffff80001000e (referenced|uptodate|dirty|head) > > I think that this is due to the lack of contiguous memory. > This test program iterates soft offlining many times for hugepages, > so finally one page in every 512MB will be removed from buddy, then we > can't allocate hugepage any more even if we have enough free pages. > This is not good for heavy hugepage users, but that should be intended. > > It seems that random.c calls madvise(MADV_SOFT_OFFLINE) for 2 hugepages, > and iterates it 1000 (==NR_LOOP) times, so if the system doesn't have > enough memory to cover the range of 2000 hugepages (1000GB in the Arm64 > system), this ENOMEM should reproduce as expected. Well, each iteration will mmap/munmap, so there should be no leaking. https://gitlab.com/cailca/linux-mm/-/blob/master/random.c#L376 It also seem to me madvise(MADV_SOFT_OFFLINE) does start to fragment memory somehow, because after this "madvise: Cannot allocate memory" happened, I immediately checked /proc/meminfo and then found no hugepage usage at all. > > > > > Reverting this patchset and its dependency patchset [2] (reverting the > > dependency alone did not help) fixed it, > > But it's still not clear to me why this was not visible before this > patchset, so I need more check for it. > > Thanks, > Naoya Horiguchi > > > > > # ./random 1 > > - start: migrate_huge_offline > > - use NUMA nodes 0,1. > > - mmap and free 2147483648 bytes hugepages on node 0 > > - mmap and free 2147483648 bytes hugepages on node 1 > > - pass: mmap_offline_node_huge > > > > [2] https://lore.kernel.org/linux-mm/1594622517-20681-1-git-send-email-iamjoonsoo.kim@xxxxxxx/ > > > > > > > > Thanks, > > > Naoya Horiguchi > > > --- > > > Previous versions: > > > v1: https://lore.kernel.org/linux-mm/1541746035-13408-1-git-send-email-n-horiguchi@xxxxxxxxxxxxx/ > > > v2: https://lore.kernel.org/linux-mm/20191017142123.24245-1-osalvador@xxxxxxx/ > > > v3: https://lore.kernel.org/linux-mm/20200624150137.7052-1-nao.horiguchi@xxxxxxxxx/ > > > v4: https://lore.kernel.org/linux-mm/20200716123810.25292-1-osalvador@xxxxxxx/ > > > --- > > > Summary: > > > > > > Naoya Horiguchi (8): > > > mm,hwpoison: cleanup unused PageHuge() check > > > mm, hwpoison: remove recalculating hpage > > > mm,madvise: call soft_offline_page() without MF_COUNT_INCREASED > > > mm,hwpoison-inject: don't pin for hwpoison_filter > > > mm,hwpoison: remove MF_COUNT_INCREASED > > > mm,hwpoison: remove flag argument from soft offline functions > > > mm,hwpoison: introduce MF_MSG_UNSPLIT_THP > > > mm,hwpoison: double-check page count in __get_any_page() > > > > > > Oscar Salvador (8): > > > mm,madvise: Refactor madvise_inject_error > > > mm,hwpoison: Un-export get_hwpoison_page and make it static > > > mm,hwpoison: Kill put_hwpoison_page > > > mm,hwpoison: Unify THP handling for hard and soft offline > > > mm,hwpoison: Rework soft offline for free pages > > > mm,hwpoison: Rework soft offline for in-use pages > > > mm,hwpoison: Refactor soft_offline_huge_page and __soft_offline_page > > > mm,hwpoison: Return 0 if the page is already poisoned in soft-offline > > > > > > drivers/base/memory.c | 2 +- > > > include/linux/mm.h | 12 +- > > > include/linux/page-flags.h | 6 +- > > > include/ras/ras_event.h | 3 + > > > mm/hwpoison-inject.c | 18 +-- > > > mm/madvise.c | 39 +++--- > > > mm/memory-failure.c | 334 ++++++++++++++++++++------------------------- > > > mm/migrate.c | 11 +- > > > mm/page_alloc.c | 60 ++++++-- > > > 9 files changed, 233 insertions(+), 252 deletions(-) > >
