From patchwork Mon Aug 14 20:53:10 2023 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: David Jeffery X-Patchwork-Id: 13353260 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 957EAEB64DD for ; Mon, 14 Aug 2023 20:55:46 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232641AbjHNUzM (ORCPT ); Mon, 14 Aug 2023 16:55:12 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:46198 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232575AbjHNUyz (ORCPT ); Mon, 14 Aug 2023 16:54:55 -0400 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.129.124]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 971D2DD for ; Mon, 14 Aug 2023 13:54:10 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1692046449; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding; bh=NfgMU/rIItqiqKT7F5SxvxS/uSYken9B9SzIQmZdl3I=; b=FXRlclNO/jHItMm8CUy4RFez8Xn3mNMHDjci0Jm3ekJqhhivkqPb1vcJEckMK8CRNj8Np+ GL2OhWtxRTsdOdMI28mnaYgOpIl6vcofSLAaQ0Yj2xdkIOAlWArSI7H7gnxVMBDWFd4O1S AGho+Ofyfkx/txV2tCB5osaTi91o+x8= Received: from mimecast-mx02.redhat.com (66.187.233.73 [66.187.233.73]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id us-mta-403-A4JzPdA0P8qZoRe19R4cnA-1; Mon, 14 Aug 2023 16:54:05 -0400 X-MC-Unique: A4JzPdA0P8qZoRe19R4cnA-1 Received: from smtp.corp.redhat.com (int-mx10.intmail.prod.int.rdu2.redhat.com [10.11.54.10]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx02.redhat.com (Postfix) with ESMTPS id 491061C2C5A9; Mon, 14 Aug 2023 20:54:05 +0000 (UTC) Received: from fedora-work.redhat.com (unknown [10.22.18.13]) by smtp.corp.redhat.com (Postfix) with ESMTP id D69B5401E6A; Mon, 14 Aug 2023 20:54:04 +0000 (UTC) From: David Jeffery To: Song Liu , linux-raid@vger.kernel.org Cc: David Jeffery , Laurence Oberman , Yu Kuai Subject: [PATCH RESEND] md: raid0: account for split bio in iostat accounting Date: Mon, 14 Aug 2023 16:53:10 -0400 Message-ID: <20230814205347.17891-1-djeffery@redhat.com> MIME-Version: 1.0 X-Scanned-By: MIMEDefang 3.1 on 10.11.54.10 Precedence: bulk List-ID: X-Mailing-List: linux-raid@vger.kernel.org When a bio is split by md raid0, the newly created bio will not be tracked by md for I/O accounting. Only the portion of I/O still assigned to the original bio which was reduced by the split will be accounted for. This results in md iostat data sometimes showing I/O values far below the actual amount of data being sent through md. md_account_bio() needs to be called for all bio generated by the bio split. Fixes: 10764815ff47 ("md: add io accounting for raid0 and raid5") Signed-off-by: David Jeffery Tested-by: Laurence Oberman Reviewed-by: Laurence Oberman Reviewed-by: Yu Kuai --- No change to the patch itself. Added Fixes and Reviewed-by lines. A simple example of the issue was generated using a raid0 device on partitions to the same device. Since all raid0 I/O then goes to one device, it makes it easy to see a gap between the md device and its sd storage. Reading an lvm device on top of the md device, the iostat output (some 0 columns and extra devices removed to make the data more compact) was: Device tps kB_read/s kB_wrtn/s kB_dscd/s kB_read md2 0.00 0.00 0.00 0.00 0 sde 0.00 0.00 0.00 0.00 0 md2 1364.00 411496.00 0.00 0.00 411496 sde 1734.00 646144.00 0.00 0.00 646144 md2 1699.00 510680.00 0.00 0.00 510680 sde 2155.00 802784.00 0.00 0.00 802784 md2 803.00 241480.00 0.00 0.00 241480 sde 1016.00 377888.00 0.00 0.00 377888 md2 0.00 0.00 0.00 0.00 0 sde 0.00 0.00 0.00 0.00 0 I/O was generated doing large direct I/O reads (12M) with dd to a linear lvm volume on top of the 4 leg raid0 device. The md2 reads were showing as roughly 2/3 of the reads to the sde device containing all of md2's raid partitions. The sum of reads to sde was 1826816 kB, which was the expected amount as it was the amount read by dd. With the patch, the total reads from md will match the reads from sde and be consistent with the amount of I/O generated. drivers/md/raid0.c | 3 +-- 1 file changed, 1 insertion(+), 2 deletions(-) diff --git a/drivers/md/raid0.c b/drivers/md/raid0.c index d1ac73fcd852..1fd559ac8c68 100644 --- a/drivers/md/raid0.c +++ b/drivers/md/raid0.c @@ -597,8 +597,7 @@ static bool raid0_make_request(struct mddev *mddev, struct bio *bio) bio = split; } - if (bio->bi_pool != &mddev->bio_set) - md_account_bio(mddev, &bio); + md_account_bio(mddev, &bio); orig_sector = sector; zone = find_zone(mddev->private, §or);