From: Qian Cai <cai@lca.pw>
To: "HORIGUCHI NAOYA(堀口 直也)" <naoya.horiguchi@nec.com>
Cc: "nao.horiguchi@gmail.com" <nao.horiguchi@gmail.com>,
"linux-mm@kvack.org" <linux-mm@kvack.org>,
"mhocko@kernel.org" <mhocko@kernel.org>,
"akpm@linux-foundation.org" <akpm@linux-foundation.org>,
"mike.kravetz@oracle.com" <mike.kravetz@oracle.com>,
"osalvador@suse.de" <osalvador@suse.de>,
"tony.luck@intel.com" <tony.luck@intel.com>,
"david@redhat.com" <david@redhat.com>,
"aneesh.kumar@linux.vnet.ibm.com"
<aneesh.kumar@linux.vnet.ibm.com>,
"zeil@yandex-team.ru" <zeil@yandex-team.ru>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH v5 00/16] HWPOISON: soft offline rework
Date: Mon, 3 Aug 2020 21:49:42 -0400 [thread overview]
Message-ID: <20200804014942.GC8894@lca.pw> (raw)
In-Reply-To: <20200804011644.GA25028@hori.linux.bs1.fc.nec.co.jp>
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@gmail.com 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@hori.linux.bs1.fc.nec.co.jp/
> >
> > 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@lge.com/
> >
> > >
> > > Thanks,
> > > Naoya Horiguchi
> > > ---
> > > Previous versions:
> > > v1: https://lore.kernel.org/linux-mm/1541746035-13408-1-git-send-email-n-horiguchi@ah.jp.nec.com/
> > > v2: https://lore.kernel.org/linux-mm/20191017142123.24245-1-osalvador@suse.de/
> > > v3: https://lore.kernel.org/linux-mm/20200624150137.7052-1-nao.horiguchi@gmail.com/
> > > v4: https://lore.kernel.org/linux-mm/20200716123810.25292-1-osalvador@suse.de/
> > > ---
> > > 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(-)
> >
next prev parent reply other threads:[~2020-08-04 1:49 UTC|newest]
Thread overview: 22+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-07-31 12:20 [PATCH v5 00/16] HWPOISON: soft offline rework nao.horiguchi
2020-07-31 12:20 ` [PATCH v5 01/16] mm,hwpoison: cleanup unused PageHuge() check nao.horiguchi
2020-07-31 12:20 ` [PATCH v5 02/16] mm, hwpoison: remove recalculating hpage nao.horiguchi
2020-07-31 12:20 ` [PATCH v5 03/16] mm,madvise: call soft_offline_page() without MF_COUNT_INCREASED nao.horiguchi
2020-07-31 12:21 ` [PATCH v5 04/16] mm,madvise: Refactor madvise_inject_error nao.horiguchi
2020-07-31 12:21 ` [PATCH v5 05/16] mm,hwpoison-inject: don't pin for hwpoison_filter nao.horiguchi
2020-07-31 12:21 ` [PATCH v5 06/16] mm,hwpoison: Un-export get_hwpoison_page and make it static nao.horiguchi
2020-07-31 12:21 ` [PATCH v5 07/16] mm,hwpoison: Kill put_hwpoison_page nao.horiguchi
2020-07-31 12:21 ` [PATCH v5 08/16] mm,hwpoison: remove MF_COUNT_INCREASED nao.horiguchi
2020-07-31 12:21 ` [PATCH v5 09/16] mm,hwpoison: remove flag argument from soft offline functions nao.horiguchi
2020-07-31 12:21 ` [PATCH v5 10/16] mm,hwpoison: Unify THP handling for hard and soft offline nao.horiguchi
2020-07-31 12:21 ` [PATCH v5 11/16] mm,hwpoison: Rework soft offline for free pages nao.horiguchi
2020-07-31 12:21 ` [PATCH v5 12/16] mm,hwpoison: Rework soft offline for in-use pages nao.horiguchi
2020-07-31 12:21 ` [PATCH v5 13/16] mm,hwpoison: Refactor soft_offline_huge_page and __soft_offline_page nao.horiguchi
2020-07-31 12:21 ` [PATCH v5 14/16] mm,hwpoison: Return 0 if the page is already poisoned in soft-offline nao.horiguchi
2020-07-31 12:21 ` [PATCH v5 15/16] mm,hwpoison: introduce MF_MSG_UNSPLIT_THP nao.horiguchi
[not found] ` <20200803123954.GA4631@lca.pw>
2020-08-03 13:36 ` [PATCH v5 00/16] HWPOISON: soft offline rework HORIGUCHI NAOYA(堀口 直也)
[not found] ` <20200803151907.GA8894@lca.pw>
2020-08-05 20:43 ` HORIGUCHI NAOYA(堀口 直也)
[not found] ` <20200803190709.GB8894@lca.pw>
2020-08-04 1:16 ` HORIGUCHI NAOYA(堀口 直也)
2020-08-04 1:49 ` Qian Cai [this message]
2020-08-04 8:13 ` osalvador
2020-08-05 20:44 ` HORIGUCHI NAOYA(堀口 直也)
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