The patch titled
Subject: thp: lazy huge zero page allocation
has been added to the -mm tree. Its filename is
thp-lazy-huge-zero-page-allocation.patch
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*** Remember to use Documentation/SubmitChecklist when testing your code ***
The -mm tree is included into linux-next and is updated
there every 3-4 working days
------------------------------------------------------
From: "Kirill A. Shutemov" <kirill.shutemov@xxxxxxxxxxxxxxx>
Subject: thp: lazy huge zero page allocation
Instead of allocating huge zero page on hugepage_init() we can postpone it
until first huge zero page map. It saves memory if THP is not in use.
cmpxchg() is used to avoid race on huge_zero_pfn initialization.
Signed-off-by: Kirill A. Shutemov <kirill.shutemov@xxxxxxxxxxxxxxx>
Cc: Andrea Arcangeli <aarcange@xxxxxxxxxx>
Cc: Andi Kleen <ak@xxxxxxxxxxxxxxx>
Cc: "H. Peter Anvin" <hpa@xxxxxxxxxxxxxxx>
Cc: Mel Gorman <mel@xxxxxxxxx>
Cc: David Rientjes <rientjes@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/huge_memory.c | 20 ++++++++++----------
1 file changed, 10 insertions(+), 10 deletions(-)
diff -puN mm/huge_memory.c~thp-lazy-huge-zero-page-allocation mm/huge_memory.c
--- a/mm/huge_memory.c~thp-lazy-huge-zero-page-allocation
+++ a/mm/huge_memory.c
@@ -161,22 +161,24 @@ static int start_khugepaged(void)
return err;
}
-static int init_huge_zero_page(void)
+static int init_huge_zero_pfn(void)
{
struct page *hpage;
+ unsigned long pfn;
hpage = alloc_pages((GFP_TRANSHUGE | __GFP_ZERO) & ~__GFP_MOVABLE,
HPAGE_PMD_ORDER);
if (!hpage)
return -ENOMEM;
-
- huge_zero_pfn = page_to_pfn(hpage);
+ pfn = page_to_pfn(hpage);
+ if (cmpxchg(&huge_zero_pfn, 0, pfn))
+ __free_page(hpage);
return 0;
}
static inline bool is_huge_zero_pfn(unsigned long pfn)
{
- return pfn == huge_zero_pfn;
+ return huge_zero_pfn && pfn == huge_zero_pfn;
}
static inline bool is_huge_zero_pmd(pmd_t pmd)
@@ -565,10 +567,6 @@ static int __init hugepage_init(void)
if (err)
return err;
- err = init_huge_zero_page();
- if (err)
- goto out;
-
err = khugepaged_slab_init();
if (err)
goto out;
@@ -591,8 +589,6 @@ static int __init hugepage_init(void)
return 0;
out:
- if (huge_zero_pfn)
- __free_page(pfn_to_page(huge_zero_pfn));
hugepage_exit_sysfs(hugepage_kobj);
return err;
}
@@ -736,6 +732,10 @@ int do_huge_pmd_anonymous_page(struct mm
return VM_FAULT_OOM;
if (!(flags & FAULT_FLAG_WRITE)) {
pgtable_t pgtable;
+ if (unlikely(!huge_zero_pfn && init_huge_zero_pfn())) {
+ count_vm_event(THP_FAULT_FALLBACK);
+ goto out;
+ }
pgtable = pte_alloc_one(mm, haddr);
if (unlikely(!pgtable))
goto out;
_
Patches currently in -mm which might be from kirill.shutemov@xxxxxxxxxxxxxxx are
linux-next.patch
mm-use-is_enabledconfig_numa-instead-of-numa_build.patch
mm-use-is_enabledconfig_compaction-instead-of-compaction_build.patch
thp-huge-zero-page-basic-preparation.patch
thp-zap_huge_pmd-zap-huge-zero-pmd.patch
thp-copy_huge_pmd-copy-huge-zero-page.patch
thp-do_huge_pmd_wp_page-handle-huge-zero-page.patch
thp-change_huge_pmd-keep-huge-zero-page-write-protected.patch
thp-change-split_huge_page_pmd-interface.patch
thp-implement-splitting-pmd-for-huge-zero-page.patch
thp-setup-huge-zero-page-on-non-write-page-fault.patch
thp-lazy-huge-zero-page-allocation.patch
thp-implement-refcounting-for-huge-zero-page.patch
thp-vmstat-implement-hzp_alloc-and-hzp_alloc_failed-events.patch
--
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