From df48a5f7a3bbac6a700026b554922943ecee1fb0 Mon Sep 17 00:00:00 2001 From: "Liam R. Howlett" Date: Tue, 31 May 2022 09:20:51 -0400 Subject: mm/page_alloc: reduce potential fragmentation in make_alloc_exact() Try to avoid using the left over split page on the next request for a page by calling __free_pages_ok() with FPI_TO_TAIL. This increases the potential of defragmenting memory when it's used for a short period of time. Link: https://lkml.kernel.org/r/20220531185626.yvlmymbxyoe5vags@revolver Signed-off-by: Liam R. Howlett Suggested-by: Matthew Wilcox (Oracle) Signed-off-by: Andrew Morton --- mm/page_alloc.c | 20 ++++++++++++-------- 1 file changed, 12 insertions(+), 8 deletions(-) (limited to 'mm/page_alloc.c') diff --git a/mm/page_alloc.c b/mm/page_alloc.c index e20ade858e71..b5a6c815ae28 100644 --- a/mm/page_alloc.c +++ b/mm/page_alloc.c @@ -5784,14 +5784,18 @@ static void *make_alloc_exact(unsigned long addr, unsigned int order, size_t size) { if (addr) { - unsigned long alloc_end = addr + (PAGE_SIZE << order); - unsigned long used = addr + PAGE_ALIGN(size); - - split_page(virt_to_page((void *)addr), order); - while (used < alloc_end) { - free_page(used); - used += PAGE_SIZE; - } + unsigned long nr = DIV_ROUND_UP(size, PAGE_SIZE); + struct page *page = virt_to_page((void *)addr); + struct page *last = page + nr; + + split_page_owner(page, 1 << order); + split_page_memcg(page, 1 << order); + while (page < --last) + set_page_refcounted(last); + + last = page + (1UL << order); + for (page += nr; page < last; page++) + __free_pages_ok(page, 0, FPI_TO_TAIL); } return (void *)addr; } -- cgit v1.2.3 From 5aae9265ee1a30cf716d6caf6b29fe99b9d55130 Mon Sep 17 00:00:00 2001 From: Hugh Dickins Date: Sat, 22 Oct 2022 00:51:06 -0700 Subject: mm: prep_compound_tail() clear page->private Although page allocation always clears page->private in the first page or head page of an allocation, it has never made a point of clearing page->private in the tails (though 0 is often what is already there). But now commit 71e2d666ef85 ("mm/huge_memory: do not clobber swp_entry_t during THP split") issues a warning when page_tail->private is found to be non-0 (unless it's swapcache). Change that warning to dump page_tail (which also dumps head), instead of just the head: so far we have seen dead000000000122, dead000000000003, dead000000000001 or 0000000000000002 in the raw output for tail private. We could just delete the warning, but today's consensus appears to want page->private to be 0, unless there's a good reason for it to be set: so now clear it in prep_compound_tail() (more general than just for THP; but not for high order allocation, which makes no pass down the tails). Link: https://lkml.kernel.org/r/1c4233bb-4e4d-5969-fbd4-96604268a285@google.com Fixes: 71e2d666ef85 ("mm/huge_memory: do not clobber swp_entry_t during THP split") Signed-off-by: Hugh Dickins Acked-by: Mel Gorman Cc: Matthew Wilcox (Oracle) Cc: Signed-off-by: Andrew Morton --- mm/huge_memory.c | 2 +- mm/page_alloc.c | 1 + 2 files changed, 2 insertions(+), 1 deletion(-) (limited to 'mm/page_alloc.c') diff --git a/mm/huge_memory.c b/mm/huge_memory.c index 03fc7e5edf07..561a42567477 100644 --- a/mm/huge_memory.c +++ b/mm/huge_memory.c @@ -2462,7 +2462,7 @@ static void __split_huge_page_tail(struct page *head, int tail, * Fix up and warn once if private is unexpectedly set. */ if (!folio_test_swapcache(page_folio(head))) { - VM_WARN_ON_ONCE_PAGE(page_tail->private != 0, head); + VM_WARN_ON_ONCE_PAGE(page_tail->private != 0, page_tail); page_tail->private = 0; } diff --git a/mm/page_alloc.c b/mm/page_alloc.c index b5a6c815ae28..218b28ee49ed 100644 --- a/mm/page_alloc.c +++ b/mm/page_alloc.c @@ -807,6 +807,7 @@ static void prep_compound_tail(struct page *head, int tail_idx) p->mapping = TAIL_MAPPING; set_compound_head(p, head); + set_page_private(p, 0); } void prep_compound_page(struct page *page, unsigned int order) -- cgit v1.2.3