From patchwork Tue Oct 6 19:15:09 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Gabriel Krisman Bertazi X-Patchwork-Id: 11819087 Return-Path: Received: from mail.kernel.org (pdx-korg-mail-1.web.codeaurora.org [172.30.200.123]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id A2E2E112E for ; Tue, 6 Oct 2020 19:15:18 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 8C750206F4 for ; Tue, 6 Oct 2020 19:15:18 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726956AbgJFTPR (ORCPT ); Tue, 6 Oct 2020 15:15:17 -0400 Received: from bhuna.collabora.co.uk ([46.235.227.227]:37992 "EHLO bhuna.collabora.co.uk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726924AbgJFTPR (ORCPT ); Tue, 6 Oct 2020 15:15:17 -0400 Received: from [127.0.0.1] (localhost [127.0.0.1]) (Authenticated sender: krisman) with ESMTPSA id D565629A897 From: Gabriel Krisman Bertazi To: axboe@kernel.dk Cc: linux-block@vger.kernel.org, ming.lei@redhat.com, Gabriel Krisman Bertazi , kernel@collabora.com, Omar Sandoval Subject: [RESEND PATCH v2] block: Consider only dispatched requests for inflight statistic Date: Tue, 6 Oct 2020 15:15:09 -0400 Message-Id: <20201006191509.2482378-1-krisman@collabora.com> X-Mailer: git-send-email 2.28.0 MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: linux-block@vger.kernel.org Hi Jens, Reviving this, hopefully for the upcoming merge window, following the suggestion that we let it sit there and see if people complain about the metric fix. As I mentioned, I'm also happy to change the documentation plus create a new in_device metric to track only requests submitted, if you prefer. Thanks, >8 According to Documentation/block/stat.rst, inflight should not include I/O requests that are in the queue but not yet dispatched to the device, but blk-mq identifies as inflight any request that has a tag allocated, which, for queues without elevator, happens at request allocation time and before it is queued in the ctx (default case in blk_mq_submit_bio). In addition, current behavior is different for queues with elevator from queues without it, since for the former the driver tag is allocated at dispatch time. A more precise approach would be to only consider requests with state MQ_RQ_IN_FLIGHT. This effectively reverts commit 6131837b1de6 ("blk-mq: count allocated but not started requests in iostats inflight") to consolidate blk-mq behavior with itself (elevator case) and with original documentation, but it differs from the behavior used by the legacy path. This version differs from v1 by using blk_mq_rq_state to access the state attribute. Avoid using blk_mq_request_started, which was suggested, since we don't want to include MQ_RQ_COMPLETE. Cc: Omar Sandoval Signed-off-by: Gabriel Krisman Bertazi --- block/blk-mq.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) +++ b/block/blk-mq.c diff --git a/block/blk-mq.c b/block/blk-mq.c index 2e4b3cad2a61..c5fefd39d0c0 100644 --- a/block/blk-mq.c