linux-kernel - [PATCH v6 2/2] mm/page_alloc: remove software prefetching in __free_pages

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Date:   Tue,  6 Nov 2018 11:33:14 +0530
From:   Arun KS <arunks@...eaurora.org>
To:     arunks.linux@...il.com, akpm@...ux-foundation.org,
        mhocko@...nel.org, vbabka@...e.cz, osalvador@...e.de,
        linux-kernel@...r.kernel.org, linux-mm@...ck.org
Cc:     getarunks@...il.com, Arun KS <arunks@...eaurora.org>
Subject: [PATCH v6 2/2] mm/page_alloc: remove software prefetching in __free_pages_core

They not only increase the code footprint, they actually make things
slower rather than faster. Remove them as contemporary hardware doesn't
need any hint.

Suggested-by: Dan Williams <dan.j.williams@...el.com>
Signed-off-by: Arun KS <arunks@...eaurora.org>
---
 mm/page_alloc.c | 6 +-----
 1 file changed, 1 insertion(+), 5 deletions(-)

diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index 7cf503f..a1b9a6a 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -1270,14 +1270,10 @@ void __free_pages_core(struct page *page, unsigned int order)
 	struct page *p = page;
 	unsigned int loop;
 
-	prefetchw(p);
-	for (loop = 0; loop < (nr_pages - 1); loop++, p++) {
-		prefetchw(p + 1);
+	for (loop = 0; loop < nr_pages ; loop++, p++) {
 		__ClearPageReserved(p);
 		set_page_count(p, 0);
 	}
-	__ClearPageReserved(p);
-	set_page_count(p, 0);
 
 	page_zone(page)->managed_pages += nr_pages;
 	set_page_refcounted(page);
-- 
1.9.1