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Date: Mon, 2 Jun 2025 07:05:14 +0200
From: Christoph Hellwig <hch@lst.de>
To: Pankaj Raghav <p.raghav@samsung.com>
Cc: Suren Baghdasaryan <surenb@google.com>,
	Ryan Roberts <ryan.roberts@arm.com>,
	Vlastimil Babka <vbabka@suse.cz>,
	Baolin Wang <baolin.wang@linux.alibaba.com>,
	Borislav Petkov <bp@alien8.de>, Ingo Molnar <mingo@redhat.com>,
	"H . Peter Anvin" <hpa@zytor.com>, Zi Yan <ziy@nvidia.com>,
	Mike Rapoport <rppt@kernel.org>,
	Dave Hansen <dave.hansen@linux.intel.com>,
	Michal Hocko <mhocko@suse.com>,
	David Hildenbrand <david@redhat.com>,
	Lorenzo Stoakes <lorenzo.stoakes@oracle.com>,
	Andrew Morton <akpm@linux-foundation.org>,
	Thomas Gleixner <tglx@linutronix.de>,
	Nico Pache <npache@redhat.com>, Dev Jain <dev.jain@arm.com>,
	"Liam R . Howlett" <Liam.Howlett@oracle.com>,
	Jens Axboe <axboe@kernel.dk>, linux-kernel@vger.kernel.org,
	linux-mm@kvack.org, linux-block@vger.kernel.org,
	willy@infradead.org, x86@kernel.org, linux-fsdevel@vger.kernel.org,
	"Darrick J . Wong" <djwong@kernel.org>, mcgrof@kernel.org,
	gost.dev@samsung.com, kernel@pankajraghav.com, hch@lst.de
Subject: Re: [RFC 3/3] block: use mm_huge_zero_folio in
 __blkdev_issue_zero_pages()
Message-ID: <20250602050514.GD21716@lst.de>
References: <20250527050452.817674-1-p.raghav@samsung.com> <20250527050452.817674-4-p.raghav@samsung.com>
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In-Reply-To: <20250527050452.817674-4-p.raghav@samsung.com>
User-Agent: Mutt/1.5.17 (2007-11-01)

On Tue, May 27, 2025 at 07:04:52AM +0200, Pankaj Raghav wrote:
> 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.

Impressive gain on the one hand - on the other hand what is the macro
workload that does a lot of zeroing on an SSD, because avoiding that
should yield even better result while reducing wear..

> +			unsigned int len, added = 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;

Unless I'm missing something the added variable can go away now, and
the code using it can simply use len.