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=-5.3 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 D060DC2B9F7 for ; Fri, 28 May 2021 16:28:48 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 9E1BC613E3 for ; Fri, 28 May 2021 16:28:48 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S236711AbhE1QaV (ORCPT ); Fri, 28 May 2021 12:30:21 -0400 Received: from mail-pg1-f170.google.com ([209.85.215.170]:37821 "EHLO mail-pg1-f170.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S234880AbhE1QaV (ORCPT ); Fri, 28 May 2021 12:30:21 -0400 Received: by mail-pg1-f170.google.com with SMTP id t193so2928643pgb.4 for ; Fri, 28 May 2021 09:28:46 -0700 (PDT) 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-language :content-transfer-encoding; bh=t+PzXrg39UDcIn84flOZlOx80R3VdZb8jorx3LvJRVM=; b=OPeTndy8j/+eugJSUKmV1EhP69dRakEU3F8EHDqoqiNtAkSCIXi80sfmZ38LD8cBAS gv8r/xBCsZBRLwGu5PCUjSMwt5ilI5uh5d9P7hKa0WRGcQBYot0nUfpBAdKDQm1UG3xC znO/sdCpaxEykskpEPz1exSDc7DCPDjLya5VKY+yYCqHYr5SpQAODgdlZtBh9WpUmLp5 LPj6ObO/nln813hgvBq2esjGV1FykEtLxbvczqzkss3HQlyAyn1fVUlpXkTfjNKTYcOK UOUvPuOw0SUl0CVBJBOFRlVfb+la0Rc2YyQuc+WzjijklrEAVpa+T/OYJFm7rPw0Hriv Zxgg== X-Gm-Message-State: AOAM531r/9Ad4hanVjgM+EIJEBWXW3bopkRcBA91D1ickeCYHDBvRxOg J+hMDPYeUmMx5LfrPQm44yst4i7VQTY= X-Google-Smtp-Source: ABdhPJzTbyyGwDqDRN6XkYXd7W9i4g0ZdxvNn1cgudLedAS2pVQgZGHrid9z4idwVrlLEUILd7ru+w== X-Received: by 2002:a65:424b:: with SMTP id d11mr9667259pgq.171.1622219325779; Fri, 28 May 2021 09:28:45 -0700 (PDT) Received: from [192.168.3.217] (c-73-241-217-19.hsd1.ca.comcast.net. [73.241.217.19]) by smtp.gmail.com with ESMTPSA id u19sm4724642pfn.158.2021.05.28.09.28.44 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Fri, 28 May 2021 09:28:45 -0700 (PDT) Subject: Re: [PATCH 0/9] Improve I/O priority support To: Wang Jianchao , Jens Axboe Cc: linux-block@vger.kernel.org, Christoph Hellwig , Jaegeuk Kim , Adam Manzanares , Paolo Valente References: <20210527010134.32448-1-bvanassche@acm.org> <22c245e9-469c-0a0f-ad31-455a33f1e073@acm.org> From: Bart Van Assche Message-ID: Date: Fri, 28 May 2021 09:28:43 -0700 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.10.2 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-block@vger.kernel.org On 5/27/21 7:05 PM, Wang Jianchao wrote: > Does it really matter that issue IO request by the order of io priority ? > > Given a device with a 32 depth queue and doesn't support io priority, even if > we issue the request by the order of io priority, will the fw of device handle > them by the same order ? Or in the other word, we always issue 32 io requests > to device one time and then the fw of device decides how to handle them. > The order of dispatching request from queue may only work when the device's > queue is full and we have a deeper queue in io scheduler. And at this moment, > maybe the user needs to check why their application saturates the block device. > > As for the qos policy of io priority, it seems similar with wbt in which read, > sync write and background write have different priority. Since we always want > the io with higher priority to be served more by the device, adapting the depth > of queue of different io priority may work ;) Hi Jianchao, Our conclusion from the extensive measurements we ran is that we cannot reach our latency goals for high-priority I/O without I/O priority support in the storage device. This is why we are working with device vendors on implementing I/O priority support in the storage devices that matter to us. Thanks, Bart.