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 8111EC54EE9 for ; Tue, 13 Sep 2022 14:20:14 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232730AbiIMOUM (ORCPT ); Tue, 13 Sep 2022 10:20:12 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:53038 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S233369AbiIMOSx (ORCPT ); Tue, 13 Sep 2022 10:18:53 -0400 Received: from mail.itouring.de (mail.itouring.de [IPv6:2a01:4f8:a0:4463::2]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 1275B27FC2 for ; Tue, 13 Sep 2022 07:13:31 -0700 (PDT) Received: from tux.applied-asynchrony.com (p5ddd7cb4.dip0.t-ipconnect.de [93.221.124.180]) by mail.itouring.de (Postfix) with ESMTPSA id 870F3103762; Tue, 13 Sep 2022 16:12:13 +0200 (CEST) Received: from [192.168.100.221] (hho.applied-asynchrony.com [192.168.100.221]) by tux.applied-asynchrony.com (Postfix) with ESMTP id 2F256F01609; Tue, 13 Sep 2022 16:12:13 +0200 (CEST) Subject: Re: wbt_lat_usec still set despite wbt disabled by BFQ To: Yu Kuai , linux-block , "yukuai (C)" , "zhangyi (F)" References: <17e0e889-e848-0bd3-3203-cb4e9b801462@huaweicloud.com> From: =?UTF-8?Q?Holger_Hoffst=c3=a4tte?= Organization: Applied Asynchrony, Inc. Message-ID: Date: Tue, 13 Sep 2022 16:12:13 +0200 MIME-Version: 1.0 In-Reply-To: <17e0e889-e848-0bd3-3203-cb4e9b801462@huaweicloud.com> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-block@vger.kernel.org On 2022-09-13 15:39, Yu Kuai wrote: > Hi, Holger > > 在 2022/08/18 1:12, Holger Hoffstätte 写道: >> >> I just noticed that my device configured with BFQ still shows wbt_lat_usec >> as configured, despite the fact that BFQ disables WBT in bfq_init_queue [1]: >> >> $cat /sys/block/sdc/queue/scheduler >> mq-deadline [bfq] none >> $cat /sys/block/sdc/queue/wbt_lat_usec >> 75000 >> >> Is this supposed to be 0 (since it's disabled) or is sysfs confused? >> >> Thanks, >> Holger > > I'm reviewing wbt codes recently, and I found that this problem will > happen if the default elevator is bfq. I'll try to fix this, do you mind > if I add reported-by tag? Do not mind at all - thank you for looking into it! Let me know if I can test a patch or help in some other way. Btw not sure what "default scheduler" means here, I set my schedulers via udev rules. In this case: ACTION=="add", KERNEL=="sd[a-z]", ATTR{queue/rotational}=="1", ATTR{queue/scheduler}="bfq" cheers Holger