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 X-Spam-Level: X-Spam-Status: No, score=-6.3 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,NICE_REPLY_A,SPF_HELO_NONE, SPF_PASS,USER_AGENT_SANE_1 autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 297ADC433E5 for ; Tue, 28 Jul 2020 07:03:24 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 069F821775 for ; Tue, 28 Jul 2020 07:03:23 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727062AbgG1HDW (ORCPT ); Tue, 28 Jul 2020 03:03:22 -0400 Received: from comms.puri.sm ([159.203.221.185]:56120 "EHLO comms.puri.sm" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726314AbgG1HDV (ORCPT ); Tue, 28 Jul 2020 03:03:21 -0400 Received: from localhost (localhost [127.0.0.1]) by comms.puri.sm (Postfix) with ESMTP id 923BBDF2A2; Tue, 28 Jul 2020 00:02:50 -0700 (PDT) Received: from comms.puri.sm ([127.0.0.1]) by localhost (comms.puri.sm [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id Ky3JeSyyrzhr; Tue, 28 Jul 2020 00:02:49 -0700 (PDT) Subject: Re: [PATCH] scsi: sd: add runtime pm to open / release To: Alan Stern , Bart Van Assche Cc: jejb@linux.ibm.com, Can Guo , martin.petersen@oracle.com, linux-scsi@vger.kernel.org, linux-kernel@vger.kernel.org, kernel@puri.sm References: <20200706164135.GE704149@rowland.harvard.edu> From: Martin Kepplinger Autocrypt: addr=martin.kepplinger@puri.sm; keydata= mQINBFULfZABEADRxJqDOYAHfrp1w8Egcv88qoru37k1x0Ugy8S6qYtKLAAt7boZW+q5gPv3 Sj2KjfkWA7gotXpASN21OIfE/puKGwhDLAySY1DGNMQ0gIVakUO0ji5GJPjeB9JlmN5hbA87 Si9k3yKQQfv7Cf9Lr1iZaV4A4yjLP/JQMImaCVdC5KyqJ98Luwci1GbsLIGX3EEjfg1+MceO 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FmxNAJx7iiXaUY9KQ3snoEz3r37RxEDcvTY9KKahwxEzk2Mf58OPVaV4PEsRianrmErSUfmp l93agbtZK1r5LaxeItFOj+O2hWFLNDenJRlBYwXwlJCiHxM/O273hZZPoP8L5p54uXhaS5EJ uV2Xzgbi3VEbw3GZr+EnDC7XNE2wUrnlD/w2W6RzVYjVT6IX4SamNlV+MWX0/1fYCutfqZl8 6BSKmJjlWpfkPKzyzjhGQVZrTZYnKAu471hRv8/6Dx5JuZJgDCnYanNx3DDreRMu/nq6TfaO ekMtxgNYb/8oDry09UFHbGHLsWn6oBo= Message-ID: Date: Tue, 28 Jul 2020 09:02:44 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.10.0 In-Reply-To: <20200706164135.GE704149@rowland.harvard.edu> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 06.07.20 18:41, Alan Stern wrote: > On Tue, Jun 30, 2020 at 20:49:58PM -0400, Alan Stern wrote: >> On Tue, Jun 30, 2020 at 04:31:58PM -0700, Bart Van Assche wrote: >>> On 2020-06-30 12:38, Alan Stern wrote: >>>> Assume that BLK_MQ_REQ_PREEMPT is set in flags. Then where exactly >>>> does blk_queue_enter(q, flags) call blk_pm_request_resume(q)? >>> >>> Please take a look at how the *current* implementation of runtime power >>> management works. Your question is relevant for the old implementation >>> of runtime power management but not for the current implementation. >> >> What do you mean by "current"? I have been looking at the implementation >> in 5.8-rc3 from Linus's tree. Should I look somewhere else? > > Any reply to this, or further concerns about the proposed patch? > > I'd like to fix up this API, and it appears that you are the only > person to have worked on it significantly in the last two years. > > Alan Stern > Hi Alan, Any API cleanup is of course welcome. I just wanted to remind you that the underlying problem: broken block device runtime pm. Your initial proposed fix "almost" did it and mounting works but during file access, it still just looks like a runtime_resume is missing somewhere. As we need to have that working at some point, I might look into it, but someone who has experience in the block layer can surely do it more efficiently. to test, turn off polling: echo 0 > /sys/module/block/parameters/events_dfl_poll_msecs and enable runtime pm in your (scsi) device: power/autosuspend_delay_ms and of course power/control (set to auto). thanks, martin