From mboxrd@z Thu Jan 1 00:00:00 1970 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 C5A3EC433EF for ; Wed, 4 May 2022 17:48:10 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1359227AbiEDRvo (ORCPT ); Wed, 4 May 2022 13:51:44 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:55272 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1357216AbiEDROz (ORCPT ); Wed, 4 May 2022 13:14:55 -0400 Received: from dfw.source.kernel.org (dfw.source.kernel.org [139.178.84.217]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 6CC1254690; Wed, 4 May 2022 09:58:25 -0700 (PDT) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by dfw.source.kernel.org (Postfix) with ESMTPS id 232B56179D; Wed, 4 May 2022 16:58:25 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 6A661C385AA; Wed, 4 May 2022 16:58:24 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1651683504; bh=DosKk7dVzX8SYgoTdF/LccHpUnW5A2jQ9D2iz4RgMQc=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=EBVG1XaU9mhV6W9L6NF/N53eJ21v4B7jTuTVvBCaUXP2pb7Mdpzf9j3nsiJ75oFZ+ ALL4husBt/Htpr7mNjRjZktkM89TnI9q9w3szLwAXOLzQ7eOHC6zh2yyKw/YeCC0SA UpXavzGoj2XJG+pwgrlAOIz+kn9GCrdJz/6b5jME= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Tejun Heo , Jens Axboe Subject: [PATCH 5.17 179/225] Revert "block: inherit request start time from bio for BLK_CGROUP" Date: Wed, 4 May 2022 18:46:57 +0200 Message-Id: <20220504153126.455057466@linuxfoundation.org> X-Mailer: git-send-email 2.36.0 In-Reply-To: <20220504153110.096069935@linuxfoundation.org> References: <20220504153110.096069935@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Tejun Heo commit 4cddeacad6d4b23493a108d0705e7d2ab89ba5a3 upstream. This reverts commit 0006707723233cb2a9a23ca19fc3d0864835704c. It has a couple problems: * bio_issue_time() is stored in bio->bi_issue truncated to 51 bits. This overflows in slightly over 26 days. Setting rq->io_start_time_ns with it means that io duration calculation would yield >26days after 26 days of uptime. This, for example, confuses kyber making it cause high IO latencies. * rq->io_start_time_ns should record the time that the IO is issued to the device so that on-device latency can be measured. However, bio_issue_time() is set before the bio goes through the rq-qos controllers (wbt, iolatency, iocost), so when the bio gets throttled in any of the mechanisms, the measured latencies make no sense - on-device latencies end up higher than request-alloc-to-completion latencies. We'll need a smarter way to avoid calling ktime_get_ns() repeatedly back-to-back. For now, let's revert the commit. Signed-off-by: Tejun Heo Cc: stable@vger.kernel.org # v5.16+ Link: https://lore.kernel.org/r/YmmeOLfo5lzc+8yI@slm.duckdns.org Signed-off-by: Jens Axboe Signed-off-by: Greg Kroah-Hartman --- block/blk-mq.c | 9 +-------- 1 file changed, 1 insertion(+), 8 deletions(-) --- a/block/blk-mq.c +++ b/block/blk-mq.c @@ -1122,14 +1122,7 @@ void blk_mq_start_request(struct request trace_block_rq_issue(rq); if (test_bit(QUEUE_FLAG_STATS, &q->queue_flags)) { - u64 start_time; -#ifdef CONFIG_BLK_CGROUP - if (rq->bio) - start_time = bio_issue_time(&rq->bio->bi_issue); - else -#endif - start_time = ktime_get_ns(); - rq->io_start_time_ns = start_time; + rq->io_start_time_ns = ktime_get_ns(); rq->stats_sectors = blk_rq_sectors(rq); rq->rq_flags |= RQF_STATS; rq_qos_issue(q, rq);