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=-7.3 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,MENTIONS_GIT_HOSTING,SPF_HELO_NONE,SPF_PASS, USER_AGENT_SANE_1 autolearn=ham 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 C05E6C43331 for ; Tue, 12 Nov 2019 13:54:48 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id A27DB2196E for ; Tue, 12 Nov 2019 13:54:48 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727412AbfKLNyr (ORCPT ); Tue, 12 Nov 2019 08:54:47 -0500 Received: from lhrrgout.huawei.com ([185.176.76.210]:2087 "EHLO huawei.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1726995AbfKLNyr (ORCPT ); Tue, 12 Nov 2019 08:54:47 -0500 Received: from lhreml705-cah.china.huawei.com (unknown [172.18.7.107]) by Forcepoint Email with ESMTP id A72B5DAB565C0B5EEC3C; Tue, 12 Nov 2019 13:54:45 +0000 (GMT) Received: from lhreml724-chm.china.huawei.com (10.201.108.75) by lhreml705-cah.china.huawei.com (10.201.108.46) with Microsoft SMTP Server (TLS) id 14.3.408.0; Tue, 12 Nov 2019 13:54:45 +0000 Received: from [127.0.0.1] (10.202.226.46) by lhreml724-chm.china.huawei.com (10.201.108.75) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.1713.5; Tue, 12 Nov 2019 13:54:45 +0000 From: John Garry Subject: Re: [PATCH 6/6] scsi: hisi_sas: Expose multiple hw queues for v3 as experimental To: Ming Lei CC: , , , , , , chenxiang References: <1571926881-75524-1-git-send-email-john.garry@huawei.com> <1571926881-75524-7-git-send-email-john.garry@huawei.com> <20191027081910.GB16704@ming.t460p> <20191112111053.GA31697@ming.t460p> Message-ID: Date: Tue, 12 Nov 2019 13:54:44 +0000 User-Agent: Mozilla/5.0 (Windows NT 10.0; WOW64; rv:68.0) Gecko/20100101 Thunderbird/68.1.2 MIME-Version: 1.0 In-Reply-To: <20191112111053.GA31697@ming.t460p> Content-Type: text/plain; charset="windows-1252"; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit X-Originating-IP: [10.202.226.46] X-ClientProxiedBy: lhreml713-chm.china.huawei.com (10.201.108.64) To lhreml724-chm.china.huawei.com (10.201.108.75) X-CFilter-Loop: Reflected Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org >> >> I mentioned in the thread "blk-mq: improvement on handling IO during CPU >> hotplug" that I was using this series to test that patchset. >> >> So just with this patchset (and without yours), I get what looks like some >> IO errors in the LLDD. The error is an underflow error. I can't figure out >> what is the cause. > Hi Ming, > Can you post the error log? Or interpret the 'underflow error' from hisi > sas or scsi viewpoint? The check here fails: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/drivers/scsi/libsas/sas_scsi_host.c?h=v5.4-rc7#n57 Indeed, no data is received. > >> >> I'm wondering if the SCSI command is getting corrupted someway. > > Why do you think the command is corrupted? I considered that the underflow may occur if we were to clobber a SCSI command/request from another hctx and zero some fields, which is detected as an underflow. But that's just guessing. However do I find if I set shost->can_queue = HISI_SAS_MAX_COMMANDS / #queues, then no issue. But maybe that's a coincidence. For this, total queue depth = HISI_SAS_MAX_COMMANDS. I don't see the impact of that. I need to test that more. > >> >>>> + if (expose_mq_experimental) { >>>> + shost->can_queue = HISI_SAS_MAX_COMMANDS; >>>> + shost->cmd_per_lun = HISI_SAS_MAX_COMMANDS; >>> The above is contradictory with current 'nr_hw_queues''s meaning, >>> see commit on Scsi_Host.nr_hw_queues. >>> >> >> Right, so I am generating the hostwide tag in the LLDD. And the Scsi >> host-wide host_busy counter should ensure that we don't pump too much IO to >> the HBA. > > Even without the host-wide host_busy, your approach should work if you > build the hisi sas tag correctly(uniquely), just not efficiently. Yes, I do that. I'd > suggest you to collect trace and observe if request with expected hisi sas > tag is sent to hardware. > I can add some debug for that. What trace do you mean? > BTW, the patch of 'scsi: core: avoid host-wide host_busy counter for scsi_mq' > will be merged to v5.5 if everything is fine. > > https://git.kernel.org/pub/scm/linux/kernel/git/mkp/scsi.git/commit/?h=5.5/scsi-queue&id=6eb045e092efefafc6687409a6fa6d1dabf0fb69 Yeah, it seems a good change. Thanks, John