Combine our previous PROT_NONE, mpol_misplaced and
migrate_misplaced_page() pieces into an effective migrate on fault
scheme.
Note that (on x86) we rely on PROT_NONE pages being !present and avoid
the TLB flush from try_to_unmap(TTU_MIGRATION). This greatly improves
the page-migration performance.
Suggested-by: Rik van Riel <riel@xxxxxxxxxx>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@xxxxxxxxx>
Reviewed-by: Rik van Riel <riel@xxxxxxxxxx>
Cc: Paul Turner <pjt@xxxxxxxxxx>
Cc: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Cc: Andrea Arcangeli <aarcange@xxxxxxxxxx>
Signed-off-by: Ingo Molnar <mingo@xxxxxxxxxx>
---
mm/huge_memory.c | 41 ++++++++++++++++++++++++++++++++++-
mm/memory.c | 63 +++++++++++++++++++++++++++++++++++++++----------------
2 files changed, 85 insertions(+), 19 deletions(-)
Index: tip/mm/huge_memory.c
===================================================================
--- tip.orig/mm/huge_memory.c
+++ tip/mm/huge_memory.c
@@ -18,6 +18,7 @@
#include <linux/freezer.h>
#include <linux/mman.h>
#include <linux/pagemap.h>
+#include <linux/migrate.h>
#include <asm/tlb.h>
#include <asm/pgalloc.h>
#include "internal.h"
@@ -741,12 +742,48 @@ void do_huge_pmd_numa_page(struct mm_str
unsigned int flags, pmd_t entry)
{
unsigned long haddr = address & HPAGE_PMD_MASK;
+ struct page *page = NULL;
+ int node;
spin_lock(&mm->page_table_lock);
if (unlikely(!pmd_same(*pmd, entry)))
goto out_unlock;
- /* do fancy stuff */
+ if (unlikely(pmd_trans_splitting(entry))) {
+ spin_unlock(&mm->page_table_lock);
+ wait_split_huge_page(vma->anon_vma, pmd);
+ return;
+ }
+
+#ifdef CONFIG_NUMA
+ page = pmd_page(entry);
+ VM_BUG_ON(!PageCompound(page) || !PageHead(page));
+
+ get_page(page);
+ spin_unlock(&mm->page_table_lock);
+
+ /*
+ * XXX should we serialize against split_huge_page ?
+ */
+
+ node = mpol_misplaced(page, vma, haddr);
+ if (node == -1)
+ goto do_fixup;
+
+ /*
+ * Due to lacking code to migrate thp pages, we'll split
+ * (which preserves the special PROT_NONE) and re-take the
+ * fault on the normal pages.
+ */
+ split_huge_page(page);
+ put_page(page);
+ return;
+
+do_fixup:
+ spin_lock(&mm->page_table_lock);
+ if (unlikely(!pmd_same(*pmd, entry)))
+ goto out_unlock;
+#endif
/* change back to regular protection */
entry = pmd_modify(entry, vma->vm_page_prot);
@@ -755,6 +792,8 @@ void do_huge_pmd_numa_page(struct mm_str
out_unlock:
spin_unlock(&mm->page_table_lock);
+ if (page)
+ put_page(page);
}
int copy_huge_pmd(struct mm_struct *dst_mm, struct mm_struct *src_mm,
Index: tip/mm/memory.c
===================================================================
--- tip.orig/mm/memory.c
+++ tip/mm/memory.c
@@ -57,6 +57,7 @@
#include <linux/swapops.h>
#include <linux/elf.h>
#include <linux/gfp.h>
+#include <linux/migrate.h>
#include <asm/io.h>
#include <asm/pgalloc.h>
@@ -1467,8 +1468,10 @@ EXPORT_SYMBOL_GPL(zap_vma_ptes);
static bool pte_numa(struct vm_area_struct *vma, pte_t pte)
{
/*
- * If we have the normal vma->vm_page_prot protections we're not a
- * 'special' PROT_NONE page.
+ * For NUMA page faults, we use PROT_NONE ptes in VMAs with
+ * "normal" vma->vm_page_prot protections. Genuine PROT_NONE
+ * VMAs should never get here, because the fault handling code
+ * will notice that the VMA has no read or write permissions.
*
* This means we cannot get 'special' PROT_NONE faults from genuine
* PROT_NONE maps, nor from PROT_WRITE file maps that do dirty
@@ -3473,35 +3476,59 @@ static int do_numa_page(struct mm_struct
unsigned long address, pte_t *ptep, pmd_t *pmd,
unsigned int flags, pte_t entry)
{
+ struct page *page = NULL;
+ int node, page_nid = -1;
spinlock_t *ptl;
- int ret = 0;
-
- if (!pte_unmap_same(mm, pmd, ptep, entry))
- goto out;
- /*
- * Do fancy stuff...
- */
-
- /*
- * OK, nothing to do,.. change the protection back to what it
- * ought to be.
- */
- ptep = pte_offset_map_lock(mm, pmd, address, &ptl);
+ ptl = pte_lockptr(mm, pmd);
+ spin_lock(ptl);
if (unlikely(!pte_same(*ptep, entry)))
- goto unlock;
+ goto out_unlock;
+
+ page = vm_normal_page(vma, address, entry);
+ if (page) {
+ get_page(page);
+ page_nid = page_to_nid(page);
+ node = mpol_misplaced(page, vma, address);
+ if (node != -1)
+ goto migrate;
+ }
+out_pte_upgrade_unlock:
flush_cache_page(vma, address, pte_pfn(entry));
ptep_modify_prot_start(mm, address, ptep);
entry = pte_modify(entry, vma->vm_page_prot);
ptep_modify_prot_commit(mm, address, ptep, entry);
+ /* No TLB flush needed because we upgraded the PTE */
+
update_mmu_cache(vma, address, ptep);
-unlock:
+
+out_unlock:
pte_unmap_unlock(ptep, ptl);
out:
- return ret;
+ if (page)
+ put_page(page);
+
+ return 0;
+
+migrate:
+ pte_unmap_unlock(ptep, ptl);
+
+ if (!migrate_misplaced_page(page, node)) {
+ page_nid = node;
+ goto out;
+ }
+
+ ptep = pte_offset_map_lock(mm, pmd, address, &ptl);
+ if (!pte_same(*ptep, entry)) {
+ put_page(page);
+ page = NULL;
+ goto out_unlock;
+ }
+
+ goto out_pte_upgrade_unlock;
}
/*
--
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