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=-2.4 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, 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 C3922C43215 for ; Fri, 22 Nov 2019 18:26:19 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 990872068F for ; Fri, 22 Nov 2019 18:26:19 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=broadcom.com header.i=@broadcom.com header.b="LExwGuLY" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726759AbfKVS0T (ORCPT ); Fri, 22 Nov 2019 13:26:19 -0500 Received: from mail-wr1-f67.google.com ([209.85.221.67]:33568 "EHLO mail-wr1-f67.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726676AbfKVS0T (ORCPT ); Fri, 22 Nov 2019 13:26:19 -0500 Received: by mail-wr1-f67.google.com with SMTP id w9so9818989wrr.0 for ; Fri, 22 Nov 2019 10:26:17 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=broadcom.com; s=google; h=subject:to:cc:references:from:message-id:date:user-agent :mime-version:in-reply-to:content-transfer-encoding:content-language; bh=Y/IHVHc1ELnmcLONQTBZ1j/UV45S8Rkhyv/6XVAgC8M=; b=LExwGuLY2hcu/Lb7XI78C+LUCJAt9IWplowRhrPHHEkgGDWz/9ANMaEVMVFVEzuGNC PjvopKvv71MvejydvDPKy3MYNNtzNHylKOj9mfMlhtBGv34veavPhEdupgp48+DXxzuM TzFRiO52XYyGj6tPaq97WGgF0Gb5hyU9hSwzs= X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:subject:to:cc:references:from:message-id:date :user-agent:mime-version:in-reply-to:content-transfer-encoding :content-language; bh=Y/IHVHc1ELnmcLONQTBZ1j/UV45S8Rkhyv/6XVAgC8M=; b=kB65K24WOBmfC2ILOfYnf2Z2YyK77ssQvitbib6XzHtdLoeX3MyWHXm91K2DPLtQH6 aR6iEC3VPi16YrhDUpkmfNHtelqOpbwxpnur3m69O9Jq+v7KrN7gPeBxYu3Fnox0AXCo cJ5gqr6tyvY8MGK2dCuZCJTfE2P1DmaaB00hlu20/VyTWxIJXBziVx6vqNX1bQrylDcj jvXoFqkFg21QBXbbl488HQifJs1YQIH1sJqOtWpnli5wCuhru10kcWjHBMibTp37kq86 KcKFMrGkS70xunBJBZ1HVOq2brZvdr1uBevIPuuGjGuHYVC4RdHONEnFLL16dmNaVJRP +NSg== X-Gm-Message-State: APjAAAWDYDWW4Y7Dyaj68OEF9ZjnAxXcI7NjbxwAXc5IyFtL6W1OTTdG 9sBLNs2YT4LlrKPFHTP63QAhvQ== X-Google-Smtp-Source: APXvYqwpDV/fQopgTPz1WnxrAmWyitWl3mUmZYllDphkr6ye73bUYmMyHcO6lj4Dw8gf0rdv/evOlQ== X-Received: by 2002:adf:db8e:: with SMTP id u14mr10316775wri.274.1574447176773; Fri, 22 Nov 2019 10:26:16 -0800 (PST) Received: from [10.69.45.46] ([192.19.223.252]) by smtp.gmail.com with ESMTPSA id c10sm4316768wml.37.2019.11.22.10.26.12 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Fri, 22 Nov 2019 10:26:15 -0800 (PST) Subject: Re: [PATCH 4/4] scsi: core: don't limit per-LUN queue depth for SSD To: Bart Van Assche , Ming Lei , Hannes Reinecke Cc: Jens Axboe , linux-block@vger.kernel.org, "James E . J . Bottomley" , "Martin K . Petersen" , linux-scsi@vger.kernel.org, Sathya Prakash , Chaitra P B , Suganath Prabu Subramani , Kashyap Desai , Sumit Saxena , Shivasharan S , "Ewan D . Milne" , Christoph Hellwig , Bart Van Assche References: <20191118103117.978-1-ming.lei@redhat.com> <20191118103117.978-5-ming.lei@redhat.com> <1081145f-3e17-9bc1-2332-50a4b5621ef7@suse.de> <20191121005323.GB24548@ming.t460p> <336f35fc-2e22-c615-9405-50297b9737ea@suse.de> <20191122080959.GC903@ming.t460p> <5f84476f-95b4-79b6-f72d-4e2de447065c@acm.org> From: James Smart Message-ID: <7e44d961-a089-e073-1e35-5890e75b0ba7@broadcom.com> Date: Fri, 22 Nov 2019 10:26:11 -0800 User-Agent: Mozilla/5.0 (Windows NT 10.0; WOW64; rv:60.0) Gecko/20100101 Thunderbird/60.9.1 MIME-Version: 1.0 In-Reply-To: <5f84476f-95b4-79b6-f72d-4e2de447065c@acm.org> Content-Type: text/plain; charset=windows-1252; format=flowed Content-Transfer-Encoding: 7bit Content-Language: en-US Sender: linux-scsi-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-scsi@vger.kernel.org On 11/22/2019 10:14 AM, Bart Van Assche wrote: > Thanks for having shared these numbers. I think this is very useful > information. Do these results show the performance drop that happens > if /sys/block/.../device/queue_depth exceeds .can_queue? What I am > wondering about is how important these results are in the context of > this discussion. Are there any modern SCSI devices for which a SCSI > LLD sets scsi_host->can_queue and scsi_host->cmd_per_lun such that the > device responds with BUSY? What surprised me is that only three SCSI > LLDs call scsi_track_queue_full() (mptsas, bfa, esp_scsi). Does that > mean that BUSY responses from a SCSI device or HBA are rare? That's because most of the drivers, which had queue full ramp up/ramp down in them and would have called scsi_track_queue_full() converted over to the moved-queue-full-handling-in-the-mid-layer, indicated by sht->track_queue_depth = 1. Yes - it is still hit a lot! -- james