From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id A4087273D89; Tue, 15 Jul 2025 18:02:49 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1752602569; cv=none; b=dIau525DhbxUlHLQ2hZwCyvhcFrjCHteaUXoigS6KyV8ZptzK04+VYzzZeht0j7C9TL7cAJRv715iOncEO5RmaknIop9/awX9yuTFBgeHcG2xh3+dLOiW9zvvb+eQZrIGj1/m4hsu1TP9if1YhchG0I1nqHBZsGsiLFZMdWZgCk= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1752602569; c=relaxed/simple; bh=Af+DxG2+ysyDU6gOtaSIdtUVvk5g9lM1d8KO0YhEd8k=; h=From:To:Cc:Subject:Date:Message-Id:MIME-Version; b=UDUkx7g7oliD+9ASIrcO8CxpI8JMQd3qwdoOF8ZFU2F3r9yKYcubqca21mCYLw3DGDWu+y63p4PW5pQodcUIc57RCv1Gr4F6UUOvpJFaUmdNC3KMzgxYgI911XHKvdNjpmmswhU4FrtRpokuhVA4rcSqOiIfjm1GJ659NUjwseQ= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=iqTCvhch; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="iqTCvhch" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 09F8DC4CEE3; Tue, 15 Jul 2025 18:02:45 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1752602569; bh=Af+DxG2+ysyDU6gOtaSIdtUVvk5g9lM1d8KO0YhEd8k=; h=From:To:Cc:Subject:Date:From; b=iqTCvhchFTCGB3V/QxGaCFh7GBj0JUvu/fGP+wMZbRnd1D4+II9DONEn5goX4z8R5 YzlgZi4ivZmWE4z0PQto4jz2ZmCqmOAC9zXNx+aBma+Z4D5cXs95LS74LPtHEQj4E1 muSH1KlN6dfiUI3krRgYH0/8NRmmOpspWhBfd2cUiqkAjOD3GqldC/HSvDVJQEygkV 23hjOhAWYUB4ffiqy4F3S7r+crDMxDCQn7/RoI/1XRJHnsYw3aRRJjT7SrH3fCLp1n NS2JOX73gZ+4F8uoPGRHOmnhtHS9XQf8LtgSYXoyXdTq1p+i2keTxvONwQHCVyOm3O X0S2RLeI2rJvQ== From: colyli@kernel.org To: linux-raid@vger.kernel.org Cc: linux-block@vger.kernel.org, Coly Li , Yu Kuai , Xiao Ni , Hannes Reinecke , Martin Wilck , Christoph Hellwig , Keith Busch Subject: [RFC PATCH] md: split bio by io_opt size in md_submit_bio() Date: Wed, 16 Jul 2025 02:02:41 +0800 Message-Id: <20250715180241.29731-1-colyli@kernel.org> X-Mailer: git-send-email 2.39.5 Precedence: bulk X-Mailing-List: linux-block@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit From: Coly Li Currently in md_submit_bio() the incoming request bio is split by bio_split_to_limits() which makes sure the bio won't exceed max_hw_sectors of a specific raid level before senting into its .make_request method. For raid level 4/5/6 such split method might be problematic and hurt large read/write perforamnce. Because limits.max_hw_sectors are not always aligned to limits.io_opt size, the split bio won't be full stripes covered on all data disks, and will introduce extra read-in I/O. Even the bio's bi_sector is aligned to limits.io_opt size and large enough, the resulted split bio is not size-friendly to corresponding raid456 level. This patch introduces bio_split_by_io_opt() to solve the above issue, 1, If the incoming bio is not limits.io_opt aligned, split the non- aligned head part. Then the next one will be aligned. 2, If the imcoming bio is limits.io_opt aligned, and split is necessary, then try to split a by multiple of limits.io_opt but not exceed limits.max_hw_sectors. Then for large bio, the sligned split part will be full-stripes covered to all data disks, no extra read-in I/Os when rmw_level is 0. And for rmw_level > 0 condistions, the limits.io_opt aligned bios are welcomed for performace as well. This RFC patch only tests on 8 disks raid5 array with 64KiB chunk size. By this patch, 64KiB chunk size for a 8 disks raid5 array, sequential write performance increases from 900MiB/s to 1.1GiB/s by fio bs=10M. If fio bs=488K (exact limits.io_opt size) the peak sequential write throughput can reach 1.51GiB/s. (Resend to include Christoph and Keith in CC list.) Signed-off-by: Coly Li Cc: Yu Kuai Cc: Xiao Ni Cc: Hannes Reinecke Cc: Martin Wilck Cc: Christoph Hellwig Cc: Keith Busch --- drivers/md/md.c | 63 ++++++++++++++++++++++++++++++++++++++++++++++++- 1 file changed, 62 insertions(+), 1 deletion(-) diff --git a/drivers/md/md.c b/drivers/md/md.c index 0f03b21e66e4..363cff633af3 100644 --- a/drivers/md/md.c +++ b/drivers/md/md.c @@ -426,6 +426,67 @@ bool md_handle_request(struct mddev *mddev, struct bio *bio) } EXPORT_SYMBOL(md_handle_request); +static struct bio *bio_split_by_io_opt(struct bio *bio) +{ + sector_t io_opt_sectors, sectors, n; + struct queue_limits lim; + struct mddev *mddev; + struct bio *split; + int level; + + mddev = bio->bi_bdev->bd_disk->private_data; + level = mddev->level; + if (level == 1 || level == 10 || level == 0 || level == LEVEL_LINEAR) + return bio_split_to_limits(bio); + + lim = mddev->gendisk->queue->limits; + io_opt_sectors = min3(bio_sectors(bio), lim.io_opt >> SECTOR_SHIFT, + lim.max_hw_sectors); + + /* No need to split */ + if (bio_sectors(bio) == io_opt_sectors) + return bio; + + n = bio->bi_iter.bi_sector; + sectors = do_div(n, io_opt_sectors); + /* Aligned to io_opt size and no need to split for radi456 */ + if (!sectors && (bio_sectors(bio) <= lim.max_hw_sectors)) + return bio; + + if (sectors) { + /** + * Not aligned to io_opt, split + * non-aligned head part. + */ + sectors = io_opt_sectors - sectors; + } else { + /** + * Aligned to io_opt, split to the largest multiple + * of io_opt within max_hw_sectors, to make full + * stripe write/read for underlying raid456 levels. + */ + n = lim.max_hw_sectors; + do_div(n, io_opt_sectors); + sectors = n * io_opt_sectors; + } + + /* Almost won't happen */ + if (unlikely(sectors >= bio_sectors(bio))) { + pr_warn("%s raid level %d: sectors %llu >= bio_sectors %u, not split\n", + __func__, level, sectors, bio_sectors(bio)); + return bio; + } + + split = bio_split(bio, sectors, GFP_NOIO, + &bio->bi_bdev->bd_disk->bio_split); + if (!split) + return bio; + split->bi_opf |= REQ_NOMERGE; + bio_chain(split, bio); + submit_bio_noacct(bio); + return split; +} + static void md_submit_bio(struct bio *bio) { const int rw = bio_data_dir(bio); @@ -441,7 +502,7 @@ static void md_submit_bio(struct bio *bio) return; } - bio = bio_split_to_limits(bio); + bio = bio_split_by_io_opt(bio); if (!bio) return; -- 2.39.5