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 | 6 +++++- 1 file changed, 5 insertions(+), 1 deletion(-)
diff --git a/mm/migrate.c b/mm/migrate.c index b0125c082549..8aa434691577 100644 --- a/mm/migrate.c +++ b/mm/migrate.c @@ -2204,9 +2204,13 @@ static int migrate_vma_collect_hole(unsigned long start, { struct migrate_vma *migrate = walk->private; unsigned long addr; + unsigned long flags; + + /* Only allow populating anonymous memory. */ + flags = vma_is_anonymous(walk->vma) ? MIGRATE_PFN_MIGRATE : 0;
for (addr = start; addr < end; addr += PAGE_SIZE) { - migrate->src[migrate->npages] = MIGRATE_PFN_MIGRATE; + migrate->src[migrate->npages] = flags; migrate->dst[migrate->npages] = 0; migrate->npages++; migrate->cpages++;