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Peter Anvin" , Vlastimil Babka , Zi Yan , Mike Rapoport , Dave Hansen , Michal Hocko , David Hildenbrand , Andrew Morton , Thomas Gleixner , Nico Pache , Dev Jain , "Liam R . Howlett" , Jens Axboe , linux-kernel@vger.kernel.org, willy@infradead.org, linux-mm@kvack.org, x86@kernel.org, linux-block@vger.kernel.org, linux-fsdevel@vger.kernel.org, "Darrick J . Wong" , mcgrof@kernel.org, gost.dev@samsung.com, hch@lst.de, Pankaj Raghav Subject: Re: [PATCH v2 5/5] block: use largest_zero_folio in __blkdev_issue_zero_pages() Message-ID: References: <20250707142319.319642-1-kernel@pankajraghav.com> <20250707142319.319642-6-kernel@pankajraghav.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Rspam-User: X-Rspamd-Server: rspam04 X-Rspamd-Queue-Id: 48205C0006 X-Stat-Signature: iyqnjddoep9atqmirftdc4wjregq6y1q X-HE-Tag: 1752672275-169338 X-HE-Meta: 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 tIeQWXaH bfnzo5pZRVuBiT5yOgnpUnB6ghfpzxqBbLRYH0t4/nXXJIxWxt8yvX4buYpEmldJFCy+cM0KgEPXN7gko4lillMi1aHOpgQ8/vOBUEoXpydnbPwr1x0rRC0J+zzXdrJFMaiNk56gN0ga1HIJ+8+COWOgcn6lsnSSqkvyQZBFbiyGd41HILxvF3cBrpvD7h1jhqDKFljBnmH+PJafwtKURgF5L/oXeX0ieqtLuCKM3DLEwu8Rmy5lRu1nbXLhUkfKhKW1kwlBkxAwmvm+XWaMqgipqSEW5AqBF48c8asOsoBx0DVZljY99pRSvB1ToyDiipEZvTrnbaAUzG3VCSptUebnjv8Mpm2/B7H7J2eYjxQdj9Y/KCRk/5ptz1pBRcn04hzAt X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Tue, Jul 15, 2025 at 05:19:54PM +0100, Lorenzo Stoakes wrote: > On Mon, Jul 07, 2025 at 04:23:19PM +0200, Pankaj Raghav (Samsung) wrote: > > From: Pankaj Raghav > > > > Use largest_zero_folio() in __blkdev_issue_zero_pages(). > > > > On systems with CONFIG_STATIC_PMD_ZERO_PAGE enabled, 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 > > --- > > block/blk-lib.c | 17 ++++++++++------- > > 1 file changed, 10 insertions(+), 7 deletions(-) > > > > diff --git a/block/blk-lib.c b/block/blk-lib.c > > index 4c9f20a689f7..70a5700b6717 100644 > > --- a/block/blk-lib.c > > +++ b/block/blk-lib.c > > @@ -196,6 +196,10 @@ 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 = largest_zero_folio(); > > Just assign this in the decl :) Yeah! > > > + > > while (nr_sects) { > > unsigned int nr_vecs = __blkdev_sectors_to_bio_pages(nr_sects); > > struct bio *bio; > > @@ -208,15 +212,14 @@ static void __blkdev_issue_zero_pages(struct block_device *bdev, > > break; > > > > do { > > - unsigned int len, added; > > + unsigned int len; > > > > - len = min_t(sector_t, > > - PAGE_SIZE, nr_sects << SECTOR_SHIFT); > > - added = bio_add_page(bio, ZERO_PAGE(0), len, 0); > > - if (added < len) > > + len = min_t(sector_t, folio_size(zero_folio), > > + nr_sects << SECTOR_SHIFT); > > + if (!bio_add_folio(bio, zero_folio, len, 0)) > > Hmm, will this work if nr_sects << SECTOR_SHIFT size isn't PMD-aligned? Yeah, that should not be a problem as long as (nr_sects << SECTOR_SHIFT) < PMD_SIZED folio. > > I guess it actually just copies individual pages in the folio as needed? > > Does this actually result in a significant performance improvement? Do we > have numbers for this to justify the series? I put it in my commit message: ``` 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. ``` Even though it is more of a synthetic benchmark, but this goes to show the effects of adding multiple bio_vecs with ZERO_PAGE instead of single PMD_ZERO_PAGE. -- Pankaj