linux-kernel - [PATCH v2 3/4] mm/vmalloc: Use kvmalloc to allocate the table of pages

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Date:   Wed, 24 Mar 2021 15:05:17 +0000
From:   "Matthew Wilcox (Oracle)" <willy@...radead.org>
To:     linux-mm@...ck.org
Cc:     "Matthew Wilcox (Oracle)" <willy@...radead.org>,
        linux-kernel@...r.kernel.org,
        Andrew Morton <akpm@...ux-foundation.org>,
        Christoph Lameter <cl@...ux.com>,
        Pekka Enberg <penberg@...nel.org>,
        David Rientjes <rientjes@...gle.com>,
        Joonsoo Kim <iamjoonsoo.kim@....com>,
        Vlastimil Babka <vbabka@...e.cz>,
        Uladzislau Rezki <urezki@...il.com>,
        Nicholas Piggin <npiggin@...il.com>
Subject: [PATCH v2 3/4] mm/vmalloc: Use kvmalloc to allocate the table of pages

If we're trying to allocate 4MB of memory, the table will be 8KiB in size
(1024 pointers * 8 bytes per pointer), which can usually be satisfied
by a kmalloc (which is significantly faster).  Instead of changing this
open-coded implementation, just use kvmalloc().

This improves the allocation speed of vmalloc(4MB) by approximately
5% in our benchmark.  It's still dominated by the 1024 calls to
alloc_pages_node(), which will be the subject of a later patch.

Signed-off-by: Matthew Wilcox (Oracle) <willy@...radead.org>
---
 mm/vmalloc.c | 7 +------
 1 file changed, 1 insertion(+), 6 deletions(-)

diff --git a/mm/vmalloc.c b/mm/vmalloc.c
index a22241e9c363..a9ed2a4b697e 100644
--- a/mm/vmalloc.c
+++ b/mm/vmalloc.c
@@ -2801,13 +2801,8 @@ static void *__vmalloc_area_node(struct vm_struct *area, gfp_t gfp_mask,
 		gfp_mask |= __GFP_HIGHMEM;
 
 	/* Please note that the recursion is strictly bounded. */
-	if (array_size > PAGE_SIZE) {
-		pages = __vmalloc_node(array_size, 1, nested_gfp, node,
+	pages = kvmalloc_node_caller(array_size, nested_gfp, node,
 					area->caller);
-	} else {
-		pages = kmalloc_node(array_size, nested_gfp, node);
-	}
-
 	if (!pages) {
 		free_vm_area(area);
 		return NULL;
-- 
2.30.2