mm: align larger anonymous mappings on THP boundaries

Align larger anonymous memory mappings on THP boundaries by going through
thp_get_unmapped_area if THPs are enabled for the current process.

With this patch, larger anonymous mappings are now THP aligned.  When a
malloc library allocates a 2MB or larger arena, that arena can now be
mapped with THPs right from the start, which can result in better TLB hit
rates and execution time.

Link: https://lkml.kernel.org/r/20220809142457.4751229f@imladris.surriel.com
Link: https://lkml.kernel.org/r/20231214223423.1133074-1-yang@os.amperecomputing.com
Signed-off-by: Rik van Riel <riel@surriel.com>
Reviewed-by: Yang Shi <shy828301@gmail.com>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Christopher Lameter <cl@linux.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

diff --git a/mm/mmap.c b/mm/mmap.c
index 1971bfffcc032f3666e28c1855718c31e5de70f3..aa82eec17489cada2a7b238ad66d09d95d89c27a 100644 (file)
--- a/mm/mmap.c
+++ b/mm/mmap.c
@@ -1829,6 +1829,9 @@ get_unmapped_area(struct file *file, unsigned long addr, unsigned long len,
                 */
                pgoff = 0;
                get_area = shmem_get_unmapped_area;
+       } else if (IS_ENABLED(CONFIG_TRANSPARENT_HUGEPAGE)) {
+               /* Ensures that larger anonymous mappings are THP aligned. */
+               get_area = thp_get_unmapped_area;
        }
 
        addr = get_area(file, addr, len, pgoff, flags);