From: Andrew Morton <akpm@linux-foundation.org>
To: akpm@linux-foundation.org, gavin.dg@linux.alibaba.com,
hughd@google.com, kirill.shutemov@linux.intel.com,
linux-mm@kvack.org, mm-commits@vger.kernel.org,
stable@vger.kernel.org, torvalds@linux-foundation.org,
willy@infradead.org, xuyu@linux.alibaba.com
Subject: [patch 10/18] mm, thp: use head page in __migration_entry_wait()
Date: Tue, 15 Jun 2021 18:23:42 -0700 [thread overview]
Message-ID: <20210616012342.r-f9_qYFs%akpm@linux-foundation.org> (raw)
In-Reply-To: <20210615182248.9a0ba90e8e66b9f4a53c0d23@linux-foundation.org>
From: Xu Yu <xuyu@linux.alibaba.com>
Subject: mm, thp: use head page in __migration_entry_wait()
We notice that hung task happens in a corner but practical scenario when
CONFIG_PREEMPT_NONE is enabled, as follows.
Process 0 Process 1 Process 2..Inf
split_huge_page_to_list
unmap_page
split_huge_pmd_address
__migration_entry_wait(head)
__migration_entry_wait(tail)
remap_page (roll back)
remove_migration_ptes
rmap_walk_anon
cond_resched
Where __migration_entry_wait(tail) is occurred in kernel space, e.g.,
copy_to_user in fstat, which will immediately fault again without
rescheduling, and thus occupy the cpu fully.
When there are too many processes performing __migration_entry_wait on
tail page, remap_page will never be done after cond_resched.
This makes __migration_entry_wait operate on the compound head page, thus
waits for remap_page to complete, whether the THP is split successfully or
roll back.
Note that put_and_wait_on_page_locked helps to drop the page reference
acquired with get_page_unless_zero, as soon as the page is on the wait
queue, before actually waiting. So splitting the THP is only prevented
for a brief interval.
Link: https://lkml.kernel.org/r/b9836c1dd522e903891760af9f0c86a2cce987eb.1623144009.git.xuyu@linux.alibaba.com
Fixes: ba98828088ad ("thp: add option to setup migration entries during PMD split")
Suggested-by: Hugh Dickins <hughd@google.com>
Signed-off-by: Gang Deng <gavin.dg@linux.alibaba.com>
Signed-off-by: Xu Yu <xuyu@linux.alibaba.com>
Acked-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Acked-by: Hugh Dickins <hughd@google.com>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---
mm/migrate.c | 1 +
1 file changed, 1 insertion(+)
--- a/mm/migrate.c~mm-thp-use-head-page-in-__migration_entry_wait
+++ a/mm/migrate.c
@@ -295,6 +295,7 @@ void __migration_entry_wait(struct mm_st
goto out;
page = migration_entry_to_page(entry);
+ page = compound_head(page);
/*
* Once page cache replacement of page migration started, page_count
_
next prev parent reply other threads:[~2021-06-16 1:23 UTC|newest]
Thread overview: 19+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-06-16 1:22 incoming Andrew Morton
2021-06-16 1:23 ` [patch 01/18] mm,hwpoison: fix race with hugetlb page allocation Andrew Morton
2021-06-16 1:23 ` [patch 02/18] mm/swap: fix pte_same_as_swp() not removing uffd-wp bit when compare Andrew Morton
2021-06-16 1:23 ` [patch 03/18] mm/slub: clarify verification reporting Andrew Morton
2021-06-16 1:23 ` [patch 04/18] mm/slub: fix redzoning for small allocations Andrew Morton
2021-06-16 1:23 ` [patch 05/18] mm/slub: actually fix freelist pointer vs redzoning Andrew Morton
2021-06-16 1:23 ` [patch 06/18] mm/hugetlb: expand restore_reserve_on_error functionality Andrew Morton
2021-06-16 1:23 ` [patch 07/18] mm/memory-failure: make sure wait for page writeback in memory_failure Andrew Morton
2021-06-16 1:23 ` [patch 08/18] crash_core, vmcoreinfo: append 'SECTION_SIZE_BITS' to vmcoreinfo Andrew Morton
2021-06-16 1:23 ` [patch 09/18] mm/slub.c: include swab.h Andrew Morton
2021-06-16 1:23 ` Andrew Morton [this message]
2021-06-16 1:23 ` [patch 11/18] mm/thp: fix __split_huge_pmd_locked() on shmem migration entry Andrew Morton
2021-06-16 1:23 ` [patch 12/18] mm/thp: make is_huge_zero_pmd() safe and quicker Andrew Morton
2021-06-16 1:23 ` [patch 13/18] mm/thp: try_to_unmap() use TTU_SYNC for safe splitting Andrew Morton
2021-06-16 1:23 ` [patch 14/18] mm/thp: fix vma_address() if virtual address below file offset Andrew Morton
2021-06-16 1:24 ` [patch 15/18] mm/thp: fix page_address_in_vma() on file THP tails Andrew Morton
2021-06-16 1:24 ` [patch 16/18] mm/thp: unmap_mapping_page() to fix THP truncate_cleanup_page() Andrew Morton
2021-06-16 1:24 ` [patch 17/18] mm: thp: replace DEBUG_VM BUG with VM_WARN when unmap fails for split Andrew Morton
2021-06-16 1:24 ` [patch 18/18] mm/sparse: fix check_usemap_section_nr warnings Andrew Morton
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