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authorJérôme Glisse <jglisse@redhat.com>2017-01-24 17:08:11 -0500
committerJérôme Glisse <jglisse@redhat.com>2017-08-09 18:13:29 -0400
commit27336ebdf7a09b4c9ad75d6ec8304e563e969fc9 (patch)
tree4ae2449ba4392d27a9d7159c3da29ba7ab3dbe28
parentf31d30da2d39c9ccbe6b1772ca3160e1d961130c (diff)
mm/migrate: migrate_vma() unmap page from vma while collecting pages
Common case for migration of virtual address range is page are map only once inside the vma in which migration is taking place. Because we already walk the CPU page table for that range we can directly do the unmap there and setup special migration swap entry. Signed-off-by: Jérôme Glisse <jglisse@redhat.com> Signed-off-by: Evgeny Baskakov <ebaskakov@nvidia.com> Signed-off-by: John Hubbard <jhubbard@nvidia.com> Signed-off-by: Mark Hairgrove <mhairgrove@nvidia.com> Signed-off-by: Sherry Cheung <SCheung@nvidia.com> Signed-off-by: Subhash Gutti <sgutti@nvidia.com>
-rw-r--r--mm/migrate.c141
1 files changed, 112 insertions, 29 deletions
diff --git a/mm/migrate.c b/mm/migrate.c
index 1e5bb524d7d8..706695b8c923 100644
--- a/mm/migrate.c
+++ b/mm/migrate.c
@@ -2111,7 +2111,7 @@ static int migrate_vma_collect_pmd(pmd_t *pmdp,
struct migrate_vma *migrate = walk->private;
struct vm_area_struct *vma = walk->vma;
struct mm_struct *mm = vma->vm_mm;
- unsigned long addr = start;
+ unsigned long addr = start, unmapped = 0;
spinlock_t *ptl;
pte_t *ptep;
@@ -2156,9 +2156,12 @@ again:
return migrate_vma_collect_hole(start, end, walk);
ptep = pte_offset_map_lock(mm, pmdp, addr, &ptl);
+ arch_enter_lazy_mmu_mode();
+
for (; addr < end; addr += PAGE_SIZE, ptep++) {
unsigned long mpfn, pfn;
struct page *page;
+ swp_entry_t entry;
pte_t pte;
pte = *ptep;
@@ -2190,11 +2193,44 @@ again:
mpfn = migrate_pfn(pfn) | MIGRATE_PFN_MIGRATE;
mpfn |= pte_write(pte) ? MIGRATE_PFN_WRITE : 0;
+ /*
+ * Optimize for the common case where page is only mapped once
+ * in one process. If we can lock the page, then we can safely
+ * set up a special migration page table entry now.
+ */
+ if (trylock_page(page)) {
+ pte_t swp_pte;
+
+ mpfn |= MIGRATE_PFN_LOCKED;
+ ptep_get_and_clear(mm, addr, ptep);
+
+ /* Setup special migration page table entry */
+ entry = make_migration_entry(page, pte_write(pte));
+ swp_pte = swp_entry_to_pte(entry);
+ if (pte_soft_dirty(pte))
+ swp_pte = pte_swp_mksoft_dirty(swp_pte);
+ set_pte_at(mm, addr, ptep, swp_pte);
+
+ /*
+ * This is like regular unmap: we remove the rmap and
+ * drop page refcount. Page won't be freed, as we took
+ * a reference just above.
+ */
+ page_remove_rmap(page, false);
+ put_page(page);
+ unmapped++;
+ }
+
next:
migrate->src[migrate->npages++] = mpfn;
}
+ arch_leave_lazy_mmu_mode();
pte_unmap_unlock(ptep - 1, ptl);
+ /* Only flush the TLB if we actually modified any entries */
+ if (unmapped)
+ flush_tlb_range(walk->vma, start, end);
+
return 0;
}
@@ -2219,7 +2255,13 @@ static void migrate_vma_collect(struct migrate_vma *migrate)
mm_walk.mm = migrate->vma->vm_mm;
mm_walk.private = migrate;
+ mmu_notifier_invalidate_range_start(mm_walk.mm,
+ migrate->start,
+ migrate->end);
walk_page_range(migrate->start, migrate->end, &mm_walk);
+ mmu_notifier_invalidate_range_end(mm_walk.mm,
+ migrate->start,
+ migrate->end);
migrate->end = migrate->start + (migrate->npages << PAGE_SHIFT);
}
@@ -2267,32 +2309,37 @@ static bool migrate_vma_check_page(struct page *page)
static void migrate_vma_prepare(struct migrate_vma *migrate)
{
const unsigned long npages = migrate->npages;
+ const unsigned long start = migrate->start;
+ unsigned long addr, i, restore = 0;
bool allow_drain = true;
- unsigned long i;
lru_add_drain();
for (i = 0; (i < npages) && migrate->cpages; i++) {
struct page *page = migrate_pfn_to_page(migrate->src[i]);
+ bool remap = true;
if (!page)
continue;
- /*
- * Because we are migrating several pages there can be
- * a deadlock between 2 concurrent migration where each
- * are waiting on each other page lock.
- *
- * Make migrate_vma() a best effort thing and backoff
- * for any page we can not lock right away.
- */
- if (!trylock_page(page)) {
- migrate->src[i] = 0;
- migrate->cpages--;
- put_page(page);
- continue;
+ if (!(migrate->src[i] & MIGRATE_PFN_LOCKED)) {
+ /*
+ * Because we are migrating several pages there can be
+ * a deadlock between 2 concurrent migration where each
+ * are waiting on each other page lock.
+ *
+ * Make migrate_vma() a best effort thing and backoff
+ * for any page we can not lock right away.
+ */
+ if (!trylock_page(page)) {
+ migrate->src[i] = 0;
+ migrate->cpages--;
+ put_page(page);
+ continue;
+ }
+ remap = false;
+ migrate->src[i] |= MIGRATE_PFN_LOCKED;
}
- migrate->src[i] |= MIGRATE_PFN_LOCKED;
if (!PageLRU(page) && allow_drain) {
/* Drain CPU's pagevec */
@@ -2301,21 +2348,50 @@ static void migrate_vma_prepare(struct migrate_vma *migrate)
}
if (isolate_lru_page(page)) {
- migrate->src[i] = 0;
- unlock_page(page);
- migrate->cpages--;
- put_page(page);
+ if (remap) {
+ migrate->src[i] &= ~MIGRATE_PFN_MIGRATE;
+ migrate->cpages--;
+ restore++;
+ } else {
+ migrate->src[i] = 0;
+ unlock_page(page);
+ migrate->cpages--;
+ put_page(page);
+ }
continue;
}
if (!migrate_vma_check_page(page)) {
- migrate->src[i] = 0;
- unlock_page(page);
- migrate->cpages--;
+ if (remap) {
+ migrate->src[i] &= ~MIGRATE_PFN_MIGRATE;
+ migrate->cpages--;
+ restore++;
- putback_lru_page(page);
+ get_page(page);
+ putback_lru_page(page);
+ } else {
+ migrate->src[i] = 0;
+ unlock_page(page);
+ migrate->cpages--;
+
+ putback_lru_page(page);
+ }
}
}
+
+ for (i = 0, addr = start; i < npages && restore; i++, addr += PAGE_SIZE) {
+ struct page *page = migrate_pfn_to_page(migrate->src[i]);
+
+ if (!page || (migrate->src[i] & MIGRATE_PFN_MIGRATE))
+ continue;
+
+ remove_migration_pte(page, migrate->vma, addr, page);
+
+ migrate->src[i] = 0;
+ unlock_page(page);
+ put_page(page);
+ restore--;
+ }
}
/*
@@ -2342,12 +2418,19 @@ static void migrate_vma_unmap(struct migrate_vma *migrate)
if (!page || !(migrate->src[i] & MIGRATE_PFN_MIGRATE))
continue;
- try_to_unmap(page, flags);
- if (page_mapped(page) || !migrate_vma_check_page(page)) {
- migrate->src[i] &= ~MIGRATE_PFN_MIGRATE;
- migrate->cpages--;
- restore++;
+ if (page_mapped(page)) {
+ try_to_unmap(page, flags);
+ if (page_mapped(page))
+ goto restore;
}
+
+ if (migrate_vma_check_page(page))
+ continue;
+
+restore:
+ migrate->src[i] &= ~MIGRATE_PFN_MIGRATE;
+ migrate->cpages--;
+ restore++;
}
for (addr = start, i = 0; i < npages && restore; addr += PAGE_SIZE, i++) {