mm: numa: Create basic numa page hinting infrastructure
Note: This patch started as "mm/mpol: Create special PROT_NONE
infrastructure" and preserves the basic idea but steals *very*
heavily from "autonuma: numa hinting page faults entry points" for
the actual fault handlers without the migration parts. The end
result is barely recognisable as either patch so all Signed-off
and Reviewed-bys are dropped. If Peter, Ingo and Andrea are ok with
this version, I will re-add the signed-offs-by to reflect the history.
In order to facilitate a lazy -- fault driven -- migration of pages, create
a special transient PAGE_NUMA variant, we can then use the 'spurious'
protection faults to drive our migrations from.
The meaning of PAGE_NUMA depends on the architecture but on x86 it is
effectively PROT_NONE. Actual PROT_NONE mappings will not generate these
NUMA faults for the reason that the page fault code checks the permission on
the VMA (and will throw a segmentation fault on actual PROT_NONE mappings),
before it ever calls handle_mm_fault.
[dhillf@gmail.com: Fix typo]
Signed-off-by: Mel Gorman <mgorman@suse.de>
Reviewed-by: Rik van Riel <riel@redhat.com>
diff --git a/mm/memory.c b/mm/memory.c
index cd8e0da..e30616f 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -3448,6 +3448,103 @@
return __do_fault(mm, vma, address, pmd, pgoff, flags, orig_pte);
}
+int do_numa_page(struct mm_struct *mm, struct vm_area_struct *vma,
+ unsigned long addr, pte_t pte, pte_t *ptep, pmd_t *pmd)
+{
+ struct page *page;
+ spinlock_t *ptl;
+
+ /*
+ * The "pte" at this point cannot be used safely without
+ * validation through pte_unmap_same(). It's of NUMA type but
+ * the pfn may be screwed if the read is non atomic.
+ *
+ * ptep_modify_prot_start is not called as this is clearing
+ * the _PAGE_NUMA bit and it is not really expected that there
+ * would be concurrent hardware modifications to the PTE.
+ */
+ ptl = pte_lockptr(mm, pmd);
+ spin_lock(ptl);
+ if (unlikely(!pte_same(*ptep, pte)))
+ goto out_unlock;
+ pte = pte_mknonnuma(pte);
+ set_pte_at(mm, addr, ptep, pte);
+ update_mmu_cache(vma, addr, ptep);
+
+ page = vm_normal_page(vma, addr, pte);
+ if (!page) {
+ pte_unmap_unlock(ptep, ptl);
+ return 0;
+ }
+
+out_unlock:
+ pte_unmap_unlock(ptep, ptl);
+ return 0;
+}
+
+/* NUMA hinting page fault entry point for regular pmds */
+#ifdef CONFIG_NUMA_BALANCING
+static int do_pmd_numa_page(struct mm_struct *mm, struct vm_area_struct *vma,
+ unsigned long addr, pmd_t *pmdp)
+{
+ pmd_t pmd;
+ pte_t *pte, *orig_pte;
+ unsigned long _addr = addr & PMD_MASK;
+ unsigned long offset;
+ spinlock_t *ptl;
+ bool numa = false;
+
+ spin_lock(&mm->page_table_lock);
+ pmd = *pmdp;
+ if (pmd_numa(pmd)) {
+ set_pmd_at(mm, _addr, pmdp, pmd_mknonnuma(pmd));
+ numa = true;
+ }
+ spin_unlock(&mm->page_table_lock);
+
+ if (!numa)
+ return 0;
+
+ /* we're in a page fault so some vma must be in the range */
+ BUG_ON(!vma);
+ BUG_ON(vma->vm_start >= _addr + PMD_SIZE);
+ offset = max(_addr, vma->vm_start) & ~PMD_MASK;
+ VM_BUG_ON(offset >= PMD_SIZE);
+ orig_pte = pte = pte_offset_map_lock(mm, pmdp, _addr, &ptl);
+ pte += offset >> PAGE_SHIFT;
+ for (addr = _addr + offset; addr < _addr + PMD_SIZE; pte++, addr += PAGE_SIZE) {
+ pte_t pteval = *pte;
+ struct page *page;
+ if (!pte_present(pteval))
+ continue;
+ if (!pte_numa(pteval))
+ continue;
+ if (addr >= vma->vm_end) {
+ vma = find_vma(mm, addr);
+ /* there's a pte present so there must be a vma */
+ BUG_ON(!vma);
+ BUG_ON(addr < vma->vm_start);
+ }
+ if (pte_numa(pteval)) {
+ pteval = pte_mknonnuma(pteval);
+ set_pte_at(mm, addr, pte, pteval);
+ }
+ page = vm_normal_page(vma, addr, pteval);
+ if (unlikely(!page))
+ continue;
+ }
+ pte_unmap_unlock(orig_pte, ptl);
+
+ return 0;
+}
+#else
+static int do_pmd_numa_page(struct mm_struct *mm, struct vm_area_struct *vma,
+ unsigned long addr, pmd_t *pmdp)
+{
+ BUG();
+}
+#endif /* CONFIG_NUMA_BALANCING */
+
/*
* These routines also need to handle stuff like marking pages dirty
* and/or accessed for architectures that don't do it in hardware (most
@@ -3486,6 +3583,9 @@
pte, pmd, flags, entry);
}
+ if (pte_numa(entry))
+ return do_numa_page(mm, vma, address, entry, pte, pmd);
+
ptl = pte_lockptr(mm, pmd);
spin_lock(ptl);
if (unlikely(!pte_same(*pte, entry)))
@@ -3554,9 +3654,11 @@
barrier();
if (pmd_trans_huge(orig_pmd)) {
- if (flags & FAULT_FLAG_WRITE &&
- !pmd_write(orig_pmd) &&
- !pmd_trans_splitting(orig_pmd)) {
+ if (pmd_numa(*pmd))
+ return do_huge_pmd_numa_page(mm, address,
+ orig_pmd, pmd);
+
+ if ((flags & FAULT_FLAG_WRITE) && !pmd_write(orig_pmd)) {
ret = do_huge_pmd_wp_page(mm, vma, address, pmd,
orig_pmd);
/*
@@ -3568,10 +3670,14 @@
goto retry;
return ret;
}
+
return 0;
}
}
+ if (pmd_numa(*pmd))
+ return do_pmd_numa_page(mm, vma, address, pmd);
+
/*
* Use __pte_alloc instead of pte_alloc_map, because we can't
* run pte_offset_map on the pmd, if an huge pmd could