linux-kernel - [RFC v2 2/2] block: use mm_huge_zero_folio in __blkdev_issue_zero

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Message-ID: <20250522090243.758943-3-p.raghav@samsung.com>
Date: Thu, 22 May 2025 11:02:43 +0200
From: Pankaj Raghav <p.raghav@...sung.com>
To: Suren Baghdasaryan <surenb@...gle.com>,
	Vlastimil Babka <vbabka@...e.cz>,
	Ryan Roberts <ryan.roberts@....com>,
	Mike Rapoport <rppt@...nel.org>,
	Michal Hocko <mhocko@...e.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Nico Pache <npache@...hat.com>,
	Dev Jain <dev.jain@....com>,
	Baolin Wang <baolin.wang@...ux.alibaba.com>,
	Borislav Petkov <bp@...en8.de>,
	Ingo Molnar <mingo@...hat.com>,
	"H . Peter Anvin" <hpa@...or.com>,
	Zi Yan <ziy@...dia.com>,
	Dave Hansen <dave.hansen@...ux.intel.com>,
	David Hildenbrand <david@...hat.com>,
	Lorenzo Stoakes <lorenzo.stoakes@...cle.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	"Liam R . Howlett" <Liam.Howlett@...cle.com>,
	Jens Axboe <axboe@...nel.dk>
Cc: linux-block@...r.kernel.org,
	linux-fsdevel@...r.kernel.org,
	"Darrick J . Wong" <djwong@...nel.org>,
	gost.dev@...sung.com,
	kernel@...kajraghav.com,
	hch@....de,
	linux-kernel@...r.kernel.org,
	linux-mm@...ck.org,
	willy@...radead.org,
	x86@...nel.org,
	mcgrof@...nel.org,
	Pankaj Raghav <p.raghav@...sung.com>
Subject: [RFC v2 2/2] block: use mm_huge_zero_folio in __blkdev_issue_zero_pages()

Use mm_huge_zero_folio in __blkdev_issue_zero_pages(). Fallback to
ZERO_PAGE if mm_huge_zero_folio is not available.

On systems that allocates mm_huge_zero_folio, we will end up sending larger
bvecs instead of multiple small ones.

Noticed a 4% increase in performance on a commercial NVMe SSD which does
not support OP_WRITE_ZEROES. The device's MDTS was 128K. The performance
gains might be bigger if the device supports bigger MDTS.

Signed-off-by: Pankaj Raghav <p.raghav@...sung.com>
---
 block/blk-lib.c | 15 +++++++++++----
 1 file changed, 11 insertions(+), 4 deletions(-)

diff --git a/block/blk-lib.c b/block/blk-lib.c
index 4c9f20a689f7..221389412359 100644
--- a/block/blk-lib.c
+++ b/block/blk-lib.c
@@ -196,6 +196,12 @@ static void __blkdev_issue_zero_pages(struct block_device *bdev,
 		sector_t sector, sector_t nr_sects, gfp_t gfp_mask,
 		struct bio **biop, unsigned int flags)
 {
+	struct folio *zero_folio;
+
+	zero_folio = mm_get_huge_zero_folio(NULL);
+	if (!zero_folio)
+		zero_folio = page_folio(ZERO_PAGE(0));
+
 	while (nr_sects) {
 		unsigned int nr_vecs = __blkdev_sectors_to_bio_pages(nr_sects);
 		struct bio *bio;
@@ -208,11 +214,12 @@ static void __blkdev_issue_zero_pages(struct block_device *bdev,
 			break;
 
 		do {
-			unsigned int len, added;
+			unsigned int len, added = 0;
 
-			len = min_t(sector_t,
-				PAGE_SIZE, nr_sects << SECTOR_SHIFT);
-			added = bio_add_page(bio, ZERO_PAGE(0), len, 0);
+			len = min_t(sector_t, folio_size(zero_folio),
+				    nr_sects << SECTOR_SHIFT);
+			if (bio_add_folio(bio, zero_folio, len, 0))
+				added = len;
 			if (added < len)
 				break;
 			nr_sects -= added >> SECTOR_SHIFT;
-- 
2.47.2