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=-15.2 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,NICE_REPLY_A,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED, USER_AGENT_SANE_1 autolearn=unavailable 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 D65C8C433FE for ; Mon, 7 Dec 2020 11:57:46 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id A47D12333F for ; Mon, 7 Dec 2020 11:57:46 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726880AbgLGL5O (ORCPT ); Mon, 7 Dec 2020 06:57:14 -0500 Received: from mx2.suse.de ([195.135.220.15]:35708 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726840AbgLGL5O (ORCPT ); Mon, 7 Dec 2020 06:57:14 -0500 X-Virus-Scanned: by amavisd-new at test-mx.suse.de Received: from relay2.suse.de (unknown [195.135.221.27]) by mx2.suse.de (Postfix) with ESMTP id DB8CFAC9A; Mon, 7 Dec 2020 11:56:32 +0000 (UTC) Subject: Re: [PATCH v2 01/17] ibmvfc: add vhost fields and defaults for MQ enablement To: Brian King , Tyrel Datwyler , james.bottomley@hansenpartnership.com Cc: martin.petersen@oracle.com, linux-scsi@vger.kernel.org, linuxppc-dev@lists.ozlabs.org, linux-kernel@vger.kernel.org, brking@linux.ibm.com References: <20201202005329.4538-1-tyreld@linux.ibm.com> <20201202005329.4538-2-tyreld@linux.ibm.com> <38903a4f-9253-0b4b-6f67-af78ec86175f@linux.ibm.com> From: Hannes Reinecke Message-ID: <6ce79011-d288-7a49-3d51-262da58d8486@suse.de> Date: Mon, 7 Dec 2020 12:56:31 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.4.0 MIME-Version: 1.0 In-Reply-To: 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-scsi@vger.kernel.org On 12/4/20 3:26 PM, Brian King wrote: > On 12/2/20 11:27 AM, Tyrel Datwyler wrote: >> On 12/2/20 7:14 AM, Brian King wrote: >>> On 12/1/20 6:53 PM, Tyrel Datwyler wrote: >>>> Introduce several new vhost fields for managing MQ state of the adapter >>>> as well as initial defaults for MQ enablement. >>>> >>>> Signed-off-by: Tyrel Datwyler >>>> --- >>>> drivers/scsi/ibmvscsi/ibmvfc.c | 9 ++++++++- >>>> drivers/scsi/ibmvscsi/ibmvfc.h | 13 +++++++++++-- >>>> 2 files changed, 19 insertions(+), 3 deletions(-) >>>> >>>> diff --git a/drivers/scsi/ibmvscsi/ibmvfc.c b/drivers/scsi/ibmvscsi/ibmvfc.c >>>> index 42e4d35e0d35..f1d677a7423d 100644 >>>> --- a/drivers/scsi/ibmvscsi/ibmvfc.c >>>> +++ b/drivers/scsi/ibmvscsi/ibmvfc.c >>>> @@ -5161,12 +5161,13 @@ static int ibmvfc_probe(struct vio_dev *vdev, const struct vio_device_id *id) >>>> } >>>> >>>> shost->transportt = ibmvfc_transport_template; >>>> - shost->can_queue = max_requests; >>>> + shost->can_queue = (max_requests / IBMVFC_SCSI_HW_QUEUES); >>> >>> This doesn't look right. can_queue is the SCSI host queue depth, not the MQ queue depth. >> >> Our max_requests is the total number commands allowed across all queues. From >> what I understand is can_queue is the total number of commands in flight allowed >> for each hw queue. >> >> /* >> * In scsi-mq mode, the number of hardware queues supported by the LLD. >> * >> * Note: it is assumed that each hardware queue has a queue depth of >> * can_queue. In other words, the total queue depth per host >> * is nr_hw_queues * can_queue. However, for when host_tagset is set, >> * the total queue depth is can_queue. >> */ >> >> We currently don't use the host wide shared tagset. > > Ok. I missed that bit... In that case, since we allocate by default only 100 > event structs. If we slice that across IBMVFC_SCSI_HW_QUEUES (16) queues, then > we end up with only about 6 commands that can be outstanding per queue, > which is going to really hurt performance... I'd suggest bumping up > IBMVFC_MAX_REQUESTS_DEFAULT from 100 to 1000 as a starting point. > Before doing that I'd rather use the host-wide shared tagset. Increasing the number of requests will increase the memory footprint of the driver (as each request will be statically allocated). Cheers, Hannes -- Dr. Hannes Reinecke Kernel Storage Architect hare@suse.de +49 911 74053 688 SUSE Software Solutions GmbH, Maxfeldstr. 5, 90409 Nürnberg HRB 36809 (AG Nürnberg), Geschäftsführer: Felix Imendörffer