linux-kernel - [RESEND PATCH] mm: align larger anonymous mappings on THP boundaries

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Date: Thu, 14 Dec 2023 14:34:23 -0800
From: Yang Shi <yang@...amperecomputing.com>
To: riel@...riel.com,
	shy828301@...il.com,
	willy@...radead.org,
	cl@...ux.com,
	akpm@...ux-foundation.org
Cc: linux-kernel@...r.kernel.org,
	linux-mm@...ck.org
Subject: [RESEND PATCH] mm: align larger anonymous mappings on THP boundaries

From: Rik van Riel <riel@...riel.com>

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
Signed-off-by: Rik van Riel <riel@...riel.com>
Reviewed-by: Yang Shi <shy828301@...il.com>
Cc: Matthew Wilcox <willy@...radead.org>
Cc: Christopher Lameter <cl@...ux.com>
Signed-off-by: Andrew Morton <akpm@...ux-foundation.org>
---
This patch was applied to v6.1, but was reverted due to a regression
report.  However it turned out the regression was not due to this patch.
I ping'ed Andrew to reapply this patch, Andrew may forget it.  This
patch helps promote THP, so I rebased it onto the latest mm-unstable.


 mm/mmap.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/mm/mmap.c b/mm/mmap.c
index 9d780f415be3..dd25a2aa94f7 100644
--- a/mm/mmap.c
+++ b/mm/mmap.c
@@ -2232,6 +2232,9 @@ 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);
-- 
2.41.0