From 0744f2807a4ffb111a31c0769878ec8b125b5241 Mon Sep 17 00:00:00 2001 From: Ralph Campbell Date: Tue, 11 Aug 2020 18:31:41 -0700 Subject: [PATCH] mm/migrate: optimize migrate_vma_setup() for holes Patch series "mm/migrate: optimize migrate_vma_setup() for holes". A simple optimization for migrate_vma_*() when the source vma is not an anonymous vma and a new test case to exercise it. This patch (of 2): 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. [rcampbell@nvidia.com: v2] Link: http://lkml.kernel.org/r/20200710194840.7602-2-rcampbell@nvidia.com Signed-off-by: Ralph Campbell Signed-off-by: Andrew Morton Cc: Jerome Glisse Cc: John Hubbard Cc: Christoph Hellwig Cc: Jason Gunthorpe Cc: "Bharata B Rao" Cc: Shuah Khan Link: http://lkml.kernel.org/r/20200710194840.7602-1-rcampbell@nvidia.com Link: http://lkml.kernel.org/r/20200709165711.26584-1-rcampbell@nvidia.com Link: http://lkml.kernel.org/r/20200709165711.26584-2-rcampbell@nvidia.com Signed-off-by: Linus Torvalds --- mm/migrate.c | 16 ++++++++++++++-- 1 file changed, 14 insertions(+), 2 deletions(-) diff --git a/mm/migrate.c b/mm/migrate.c index 819e55130134..b52f30113366 100644 --- a/mm/migrate.c +++ b/mm/migrate.c @@ -2168,6 +2168,16 @@ 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; @@ -2260,8 +2270,10 @@ again: 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; } -- 2.39.5