diff mbox series

[v2,1/2] mm/migrate: optimize migrate_vma_setup() for holes

Message ID 20200710194840.7602-2-rcampbell@nvidia.com (mailing list archive)
State Mainlined
Commit 0744f2807a4ffb111a31c0769878ec8b125b5241
Headers show
Series mm/migrate: optimize migrate_vma_setup() for holes | expand

Commit Message

Ralph Campbell July 10, 2020, 7:48 p.m. UTC
When migrating system memory to device private memory, if the source
address range is a valid VMA range and there is no memory or a zero page,
the source PFN array is marked as valid but with no PFN. This lets the
device driver allocate private memory and clear it, then insert the new
device private struct page into the CPU's page tables when
migrate_vma_pages() is called. migrate_vma_pages() only inserts the
new page if the VMA is an anonymous range. There is no point in telling
the device driver to allocate device private memory and then not migrate
the page. Instead, mark the source PFN array entries as not migrating to
avoid this overhead.

Signed-off-by: Ralph Campbell <rcampbell@nvidia.com>
---
 mm/migrate.c | 16 ++++++++++++++--
 1 file changed, 14 insertions(+), 2 deletions(-)
diff mbox series

Patch

diff --git a/mm/migrate.c b/mm/migrate.c
index b0125c082549..ec00b7a6ea2a 100644
--- a/mm/migrate.c
+++ b/mm/migrate.c
@@ -2205,6 +2205,16 @@  static int migrate_vma_collect_hole(unsigned long start,
 	struct migrate_vma *migrate = walk->private;
 	unsigned long addr;
 
+	/* Only allow populating anonymous memory. */
+	if (!vma_is_anonymous(walk->vma)) {
+		for (addr = start; addr < end; addr += PAGE_SIZE) {
+			migrate->src[migrate->npages] = 0;
+			migrate->dst[migrate->npages] = 0;
+			migrate->npages++;
+		}
+		return 0;
+	}
+
 	for (addr = start; addr < end; addr += PAGE_SIZE) {
 		migrate->src[migrate->npages] = MIGRATE_PFN_MIGRATE;
 		migrate->dst[migrate->npages] = 0;
@@ -2297,8 +2307,10 @@  static int migrate_vma_collect_pmd(pmd_t *pmdp,
 		pte = *ptep;
 
 		if (pte_none(pte)) {
-			mpfn = MIGRATE_PFN_MIGRATE;
-			migrate->cpages++;
+			if (vma_is_anonymous(vma)) {
+				mpfn = MIGRATE_PFN_MIGRATE;
+				migrate->cpages++;
+			}
 			goto next;
 		}