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=-2.6 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,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 5AA02C76191 for ; Thu, 18 Jul 2019 13:59:21 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 22F7B217F4 for ; Thu, 18 Jul 2019 13:59:21 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1563458361; bh=L4yAaascoYhpqh8x2UbwZPouQnIJwaSBPbDdsN9uRjI=; h=Date:From:To:Subject:References:In-Reply-To:List-ID:From; b=QLxgtYp8wohqCy+p9mXSG/9chSVmWYqkcCwPIMbG92VrZXsTbGfyCDO1aoEJyBIWc gIRy5AGRN/pAhNuUQxIF19MJfFspdAyCvUxZtpXxlVd7iqODOBx3uCR6j7DQl2vg9l t/9F/gAPWFV3SUpvYxCg8/ZOJFMRXCgVyHBIBVi8= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727733AbfGRN7U (ORCPT ); Thu, 18 Jul 2019 09:59:20 -0400 Received: from mail-pl1-f193.google.com ([209.85.214.193]:37325 "EHLO mail-pl1-f193.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726608AbfGRN7U (ORCPT ); Thu, 18 Jul 2019 09:59:20 -0400 Received: by mail-pl1-f193.google.com with SMTP id b3so13946659plr.4; Thu, 18 Jul 2019 06:59:19 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=sender:date:from:to:subject:message-id:references:mime-version :content-disposition:in-reply-to:user-agent; bh=NUBO4YCRDgiN4UTvulVlnqUREX1vo2A5l3XRIoGqGME=; b=HB2wxzPrDEbYvHZRxbCo9QRYUEqFFdl/rLdSPDNQYHaEXWjZkxMi5D3ZDvSHU+GimH SjcBOAyXrOFaRY0/xrjsItgWCiNyLkHR22zMFkHeN5NIyS9rLfXrSGDxiRtB3m76QUSe /zMrEvjf8vwCUkix56WOcpeoCu3cMSS8jTI5uDV9f7v2E+6pf01BfrasSPbmS1t2lb0d jIylXQGdbBV6wsnHLlR0FIX4ZevsifJ+0fXpE9MeaNqosdEUDzHJZmINobNAcB5l20d8 C+arXOCsEGPjD+C3b/NqjC0jhOHPsaVVIwQx0NzkHOVSIdU5STuQzJ1UChfJRB7Mhe9y dbyw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:sender:date:from:to:subject:message-id :references:mime-version:content-disposition:in-reply-to:user-agent; bh=NUBO4YCRDgiN4UTvulVlnqUREX1vo2A5l3XRIoGqGME=; b=fvSLcgTL6BK0k1H/x/TiRCGME4y7Iyd9IVib1+OC6syqTdV0V+SUYR3nJ3DyMck3yL hM2K2Vm6C7ScTh4Q6bdHrHFHIYKJpqKiNwCQYdF8OBs3PMPnKvmB3ts4XyTaHAVL2Kvl v8LwWulHa898iuwetIcv0LpsUUGFc2VkLvXVI5GeU0Y7kFtOe3h3iF4nFthyD+mJiCoG VcNYxiAzjetfi2xptnpNV4awsOhPijoZkrA+QseDB9HxH/wwAY4N7NlzU0GM9DKJRorZ ijRc8hnAJY0FblhLbuO+uC8EadoR2425nXSahTVQj/q34bP3N+gXIAxufzcVN8BT0CSC s4cA== X-Gm-Message-State: APjAAAWOWIHuHTuH8YGMEYDqlPo5CTeChBzcemrS5rdqU4NbYTHCU1tI pgM6o+eGGnVpNbX9+mxV5s8= X-Google-Smtp-Source: APXvYqx173fSB7lx9dKAPXlsiipxa5JyR/hpYuhUgImVW+wGnZmLIzDlKvpQwh4ZL+yVrTeDqFz9yg== X-Received: by 2002:a17:902:5c3:: with SMTP id f61mr46783088plf.98.1563458359244; Thu, 18 Jul 2019 06:59:19 -0700 (PDT) Received: from localhost ([2620:10d:c091:500::3:ef9b]) by smtp.gmail.com with ESMTPSA id e11sm33141264pfm.35.2019.07.18.06.59.18 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Thu, 18 Jul 2019 06:59:18 -0700 (PDT) Date: Thu, 18 Jul 2019 06:59:16 -0700 From: Tejun Heo To: axboe@kernel.dk, hch@lst.de, bvanassche@acm.org, keith.busch@intel.com, minwoo.im.dev@gmail.com, linux-block@vger.kernel.org, cgroups@vger.kernel.org, linux-nvme@lists.infradead.org Subject: Re: [PATCH v3 1/5] block: add weighted round robin for blkcgroup Message-ID: <20190718135916.GC696309@devbig004.ftw2.facebook.com> References: <1333161d2c64dbe93f9dcd0814ffaf6d00216d58.1561385989.git.zhangweiping@didiglobal.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1333161d2c64dbe93f9dcd0814ffaf6d00216d58.1561385989.git.zhangweiping@didiglobal.com> User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-block-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-block@vger.kernel.org Hello, Weiping. On Mon, Jun 24, 2019 at 10:28:51PM +0800, Weiping Zhang wrote: > +static const char *blk_wrr_name[BLK_WRR_COUNT] = { > + [BLK_WRR_NONE] = "none", > + [BLK_WRR_LOW] = "low", > + [BLK_WRR_MEDIUM] = "medium", > + [BLK_WRR_HIGH] = "high", > + [BLK_WRR_URGENT] = "urgent", > +}; cgroup controllers must be fully hierarchical which the proposed implementation isn't. While it can be made hierarchical, there's only so much one can do if there are only five priority levels. Can you please take a look at the following? http://lkml.kernel.org/r/20190710205128.1316483-1-tj@kernel.org In comparison, I'm having a bit of hard time seeing the benefits of this approach. In addition to the finite level limitation, the actual WRR behavior would be device dependent and what each level means is likely to fluctuate depending on the workload and device model. I wonder whether WRR is something more valuable to help internal queue management rather than being exposed to userspace directly. Thanks. -- tejun