From: Hugh Dickins <hughd@google.com>
To: Andrew Morton <akpm@linux-foundation.org>
Cc: Mike Kravetz <mike.kravetz@oracle.com>,
Mike Rapoport <rppt@kernel.org>,
"Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>,
Matthew Wilcox <willy@infradead.org>,
David Hildenbrand <david@redhat.com>,
Suren Baghdasaryan <surenb@google.com>,
Qi Zheng <zhengqi.arch@bytedance.com>,
Yang Shi <shy828301@gmail.com>,
Mel Gorman <mgorman@techsingularity.net>,
Peter Xu <peterx@redhat.com>,
Peter Zijlstra <peterz@infradead.org>,
Will Deacon <will@kernel.org>, Yu Zhao <yuzhao@google.com>,
Alistair Popple <apopple@nvidia.com>,
Ralph Campbell <rcampbell@nvidia.com>,
Ira Weiny <ira.weiny@intel.com>,
Steven Price <steven.price@arm.com>,
SeongJae Park <sj@kernel.org>,
Naoya Horiguchi <naoya.horiguchi@nec.com>,
Christophe Leroy <christophe.leroy@csgroup.eu>,
Zack Rusin <zackr@vmware.com>, Jason Gunthorpe <jgg@ziepe.ca>,
Axel Rasmussen <axelrasmussen@google.com>,
Anshuman Khandual <anshuman.khandual@arm.com>,
Pasha Tatashin <pasha.tatashin@soleen.com>,
Miaohe Lin <linmiaohe@huawei.com>,
Minchan Kim <minchan@kernel.org>,
Christoph Hellwig <hch@infradead.org>,
Song Liu <song@kernel.org>,
Thomas Hellstrom <thomas.hellstrom@linux.intel.com>,
Russell King <linux@armlinux.org.uk>,
"David S. Miller" <davem@davemloft.net>,
Michael Ellerman <mpe@ellerman.id.au>,
"Aneesh Kumar K.V" <aneesh.kumar@linux.ibm.com>,
Heiko Carstens <hca@linux.ibm.com>,
Christian Borntraeger <borntraeger@linux.ibm.com>,
Claudio Imbrenda <imbrenda@linux.ibm.com>,
Alexander Gordeev <agordeev@linux.ibm.com>,
Jann Horn <jannh@google.com>,
linux-arm-kernel@lists.infradead.org,
sparclinux@vger.kernel.org, linuxppc-dev@lists.ozlabs.org,
linux-s390@vger.kernel.org, linux-kernel@vger.kernel.org,
linux-mm@kvack.org
Subject: [PATCH 11/12] mm/khugepaged: delete khugepaged_collapse_pte_mapped_thps()
Date: Sun, 28 May 2023 23:28:52 -0700 (PDT) [thread overview]
Message-ID: <1bf6f10-1f8d-d410-98b9-66cbf9a45c2@google.com> (raw)
In-Reply-To: <35e983f5-7ed3-b310-d949-9ae8b130cdab@google.com>
Now that retract_page_tables() can retract page tables reliably, without
depending on trylocks, delete all the apparatus for khugepaged to try
again later: khugepaged_collapse_pte_mapped_thps() etc; and free up the
per-mm memory which was set aside for that in the khugepaged_mm_slot.
But one part of that is worth keeping: when hpage_collapse_scan_file()
found SCAN_PTE_MAPPED_HUGEPAGE, that address was noted in the mm_slot
to be tried for retraction later - catching, for example, page tables
where a reversible mprotect() of a portion had required splitting the
pmd, but now it can be recollapsed. Call collapse_pte_mapped_thp()
directly in this case (why was it deferred before? I assume an issue
with needing mmap_lock for write, but now it's only needed for read).
Signed-off-by: Hugh Dickins <hughd@google.com>
---
mm/khugepaged.c | 125 +++++++-----------------------------------------
1 file changed, 16 insertions(+), 109 deletions(-)
diff --git a/mm/khugepaged.c b/mm/khugepaged.c
index 2999500abdd5..301c0e54a2ef 100644
--- a/mm/khugepaged.c
+++ b/mm/khugepaged.c
@@ -92,8 +92,6 @@ static __read_mostly DEFINE_HASHTABLE(mm_slots_hash, MM_SLOTS_HASH_BITS);
static struct kmem_cache *mm_slot_cache __read_mostly;
-#define MAX_PTE_MAPPED_THP 8
-
struct collapse_control {
bool is_khugepaged;
@@ -107,15 +105,9 @@ struct collapse_control {
/**
* struct khugepaged_mm_slot - khugepaged information per mm that is being scanned
* @slot: hash lookup from mm to mm_slot
- * @nr_pte_mapped_thp: number of pte mapped THP
- * @pte_mapped_thp: address array corresponding pte mapped THP
*/
struct khugepaged_mm_slot {
struct mm_slot slot;
-
- /* pte-mapped THP in this mm */
- int nr_pte_mapped_thp;
- unsigned long pte_mapped_thp[MAX_PTE_MAPPED_THP];
};
/**
@@ -1441,50 +1433,6 @@ static void collect_mm_slot(struct khugepaged_mm_slot *mm_slot)
}
#ifdef CONFIG_SHMEM
-/*
- * Notify khugepaged that given addr of the mm is pte-mapped THP. Then
- * khugepaged should try to collapse the page table.
- *
- * Note that following race exists:
- * (1) khugepaged calls khugepaged_collapse_pte_mapped_thps() for mm_struct A,
- * emptying the A's ->pte_mapped_thp[] array.
- * (2) MADV_COLLAPSE collapses some file extent with target mm_struct B, and
- * retract_page_tables() finds a VMA in mm_struct A mapping the same extent
- * (at virtual address X) and adds an entry (for X) into mm_struct A's
- * ->pte-mapped_thp[] array.
- * (3) khugepaged calls khugepaged_collapse_scan_file() for mm_struct A at X,
- * sees a pte-mapped THP (SCAN_PTE_MAPPED_HUGEPAGE) and adds an entry
- * (for X) into mm_struct A's ->pte-mapped_thp[] array.
- * Thus, it's possible the same address is added multiple times for the same
- * mm_struct. Should this happen, we'll simply attempt
- * collapse_pte_mapped_thp() multiple times for the same address, under the same
- * exclusive mmap_lock, and assuming the first call is successful, subsequent
- * attempts will return quickly (without grabbing any additional locks) when
- * a huge pmd is found in find_pmd_or_thp_or_none(). Since this is a cheap
- * check, and since this is a rare occurrence, the cost of preventing this
- * "multiple-add" is thought to be more expensive than just handling it, should
- * it occur.
- */
-static bool khugepaged_add_pte_mapped_thp(struct mm_struct *mm,
- unsigned long addr)
-{
- struct khugepaged_mm_slot *mm_slot;
- struct mm_slot *slot;
- bool ret = false;
-
- VM_BUG_ON(addr & ~HPAGE_PMD_MASK);
-
- spin_lock(&khugepaged_mm_lock);
- slot = mm_slot_lookup(mm_slots_hash, mm);
- mm_slot = mm_slot_entry(slot, struct khugepaged_mm_slot, slot);
- if (likely(mm_slot && mm_slot->nr_pte_mapped_thp < MAX_PTE_MAPPED_THP)) {
- mm_slot->pte_mapped_thp[mm_slot->nr_pte_mapped_thp++] = addr;
- ret = true;
- }
- spin_unlock(&khugepaged_mm_lock);
- return ret;
-}
-
/* hpage must be locked, and mmap_lock must be held */
static int set_huge_pmd(struct vm_area_struct *vma, unsigned long addr,
pmd_t *pmdp, struct page *hpage)
@@ -1675,29 +1623,6 @@ int collapse_pte_mapped_thp(struct mm_struct *mm, unsigned long addr,
goto drop_hpage;
}
-static void khugepaged_collapse_pte_mapped_thps(struct khugepaged_mm_slot *mm_slot)
-{
- struct mm_slot *slot = &mm_slot->slot;
- struct mm_struct *mm = slot->mm;
- int i;
-
- if (likely(mm_slot->nr_pte_mapped_thp == 0))
- return;
-
- if (!mmap_write_trylock(mm))
- return;
-
- if (unlikely(hpage_collapse_test_exit(mm)))
- goto out;
-
- for (i = 0; i < mm_slot->nr_pte_mapped_thp; i++)
- collapse_pte_mapped_thp(mm, mm_slot->pte_mapped_thp[i], false);
-
-out:
- mm_slot->nr_pte_mapped_thp = 0;
- mmap_write_unlock(mm);
-}
-
static void retract_page_tables(struct address_space *mapping, pgoff_t pgoff)
{
struct vm_area_struct *vma;
@@ -2326,16 +2251,6 @@ static int hpage_collapse_scan_file(struct mm_struct *mm, unsigned long addr,
{
BUILD_BUG();
}
-
-static void khugepaged_collapse_pte_mapped_thps(struct khugepaged_mm_slot *mm_slot)
-{
-}
-
-static bool khugepaged_add_pte_mapped_thp(struct mm_struct *mm,
- unsigned long addr)
-{
- return false;
-}
#endif
static unsigned int khugepaged_scan_mm_slot(unsigned int pages, int *result,
@@ -2365,7 +2280,6 @@ static unsigned int khugepaged_scan_mm_slot(unsigned int pages, int *result,
khugepaged_scan.mm_slot = mm_slot;
}
spin_unlock(&khugepaged_mm_lock);
- khugepaged_collapse_pte_mapped_thps(mm_slot);
mm = slot->mm;
/*
@@ -2418,36 +2332,29 @@ static unsigned int khugepaged_scan_mm_slot(unsigned int pages, int *result,
khugepaged_scan.address);
mmap_read_unlock(mm);
- *result = hpage_collapse_scan_file(mm,
- khugepaged_scan.address,
- file, pgoff, cc);
mmap_locked = false;
+ *result = hpage_collapse_scan_file(mm,
+ khugepaged_scan.address, file, pgoff, cc);
+ if (*result == SCAN_PTE_MAPPED_HUGEPAGE) {
+ mmap_read_lock(mm);
+ mmap_locked = true;
+ if (hpage_collapse_test_exit(mm)) {
+ fput(file);
+ goto breakouterloop;
+ }
+ *result = collapse_pte_mapped_thp(mm,
+ khugepaged_scan.address, false);
+ if (*result == SCAN_PMD_MAPPED)
+ *result = SCAN_SUCCEED;
+ }
fput(file);
} else {
*result = hpage_collapse_scan_pmd(mm, vma,
- khugepaged_scan.address,
- &mmap_locked,
- cc);
+ khugepaged_scan.address, &mmap_locked, cc);
}
- switch (*result) {
- case SCAN_PTE_MAPPED_HUGEPAGE: {
- pmd_t *pmd;
- *result = find_pmd_or_thp_or_none(mm,
- khugepaged_scan.address,
- &pmd);
- if (*result != SCAN_SUCCEED)
- break;
- if (!khugepaged_add_pte_mapped_thp(mm,
- khugepaged_scan.address))
- break;
- } fallthrough;
- case SCAN_SUCCEED:
+ if (*result == SCAN_SUCCEED)
++khugepaged_pages_collapsed;
- break;
- default:
- break;
- }
/* move to next address */
khugepaged_scan.address += HPAGE_PMD_SIZE;
--
2.35.3
next prev parent reply other threads:[~2023-05-29 6:29 UTC|newest]
Thread overview: 27+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-05-29 6:11 [PATCH 00/12] mm: free retracted page table by RCU Hugh Dickins
2023-05-29 6:14 ` [PATCH 01/12] mm/pgtable: add rcu_read_lock() and rcu_read_unlock()s Hugh Dickins
2023-05-31 17:06 ` Jann Horn
2023-05-29 6:16 ` [PATCH 02/12] mm/pgtable: add PAE safety to __pte_offset_map() Hugh Dickins
2023-05-29 13:56 ` Matthew Wilcox
2023-05-29 6:17 ` [PATCH 03/12] arm: adjust_pte() use pte_offset_map_nolock() Hugh Dickins
2023-05-29 6:18 ` [PATCH 04/12] powerpc: assert_pte_locked() " Hugh Dickins
2023-05-29 6:20 ` [PATCH 05/12] powerpc: add pte_free_defer() for pgtables sharing page Hugh Dickins
2023-05-29 14:02 ` Matthew Wilcox
2023-05-29 14:36 ` Hugh Dickins
[not found] ` <ZHn6n5eVTsr4Wl8x@ziepe.ca>
[not found] ` <4df4909f-f5dd-6f94-9792-8f2949f542b3@google.com>
[not found] ` <ZH95oobIqN0WO5MK@ziepe.ca>
[not found] ` <ZH+DAxLhIYpTlIFc@x1n>
[not found] ` <ZH+EMp9RuEVOjVNb@ziepe.ca>
2023-06-07 3:49 ` Hugh Dickins
2023-05-29 6:21 ` [PATCH 06/12] sparc: " Hugh Dickins
2023-05-29 6:22 ` [PATCH 07/12] s390: add pte_free_defer(), with use of mmdrop_async() Hugh Dickins
[not found] ` <175ebec8-761-c3f-2d98-6c3bd87161c8@google.com>
2023-06-06 19:40 ` Gerald Schaefer
2023-06-08 3:35 ` Hugh Dickins
2023-06-08 13:58 ` Jason Gunthorpe
2023-06-08 15:47 ` Gerald Schaefer
[not found] ` <ZH99cLKeALvUCIH8@ziepe.ca>
2023-06-08 2:46 ` Hugh Dickins
2023-05-29 6:23 ` [PATCH 08/12] mm/pgtable: add pte_free_defer() for pgtable as page Hugh Dickins
2023-05-29 6:25 ` [PATCH 09/12] mm/khugepaged: retract_page_tables() without mmap or vma lock Hugh Dickins
2023-05-29 23:26 ` Peter Xu
2023-05-31 0:38 ` Hugh Dickins
2023-05-31 15:34 ` Jann Horn
2023-05-29 6:26 ` [PATCH 10/12] mm/khugepaged: collapse_pte_mapped_thp() with mmap_read_lock() Hugh Dickins
2023-05-31 17:25 ` Jann Horn
2023-05-29 6:28 ` Hugh Dickins [this message]
2023-05-29 6:30 ` [PATCH 12/12] mm: delete mmap_write_trylock() and vma_try_start_write() Hugh Dickins
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