Revert "mm: align larger anonymous mappings on THP boundaries"

This reverts commit f35b5d7d676e59e401690b678cd3cfec5e785c23.

It has been reported to cause huge performance regressions on some loads
(will-it-scale.per_process_ops, but also building the kernel with
clang).

The commit did speed up gcc builds by a small amount, so it's not an
unambiguous regression, but until the big regressions are understood,
let's revert it.

Reported-by: kernel test robot <yujie.liu@intel.com>
Link: https://lore.kernel.org/r/202210181535.7144dd15-yujie.liu@intel.com
Reported-by: Nathan Chancellor <nathan@kernel.org>
Link: https://lore.kernel.org/lkml/Y1DNQaoPWxE%2BrGce@dev-arch.thelio-3990X/
Cc: Huang, Ying <ying.huang@intel.com>
Cc: Rik van Riel <riel@surriel.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Yang Shi <shy828301@gmail.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/mm/mmap.c b/mm/mmap.c
index 74a84eb..a5eb2f1 100644 (file)
--- a/mm/mmap.c
+++ b/mm/mmap.c
@@ -1779,9 +1779,6 @@ 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);