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 Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 8FBE0C433F5 for ; Thu, 29 Sep 2022 15:06:00 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender:List-Subscribe:List-Help :List-Post:List-Archive:List-Unsubscribe:List-Id:Content-Transfer-Encoding: Content-Type:In-Reply-To:From:References:Cc:To:Subject:MIME-Version:Date: Message-ID:Reply-To:Content-ID:Content-Description:Resent-Date:Resent-From: Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Owner; bh=jgnDNASof/g3kUSSX5icXdxlDgaWwUplvsCMn1pF5vM=; b=AWy28WRHJELlXi4a9GZDLHN2mz b8D2l0npjcTDgPEYulpcnbvf7iP4If9IWYzIIEmx5xio4ljiePBbACQBUAGdCfykqbX1JNAunrCTH 3e/NfJSjsrNJTtKFuYTOXU7q46Tklafj4dqgTdh4fhJfwCz4Jy5jJpcdr8fGU4CHZ38rIjLCfpseT SCuFSvWNrlZ5AMSLd/la3CmIZe7RkATsWRAqRe3cAGP5FUTT0Vmo0lxEkNPL7oq/5VgjRNCZl88kp DGb4iWSfWOd1pDbZaAee0gvoVZJX0SKfilQ/tvxN++V0lPOm/q4yUvHkVnJ72GhFTLtXHydiJGA2P n0hjBPJg==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.94.2 #2 (Red Hat Linux)) id 1odv6r-003lDi-MH; Thu, 29 Sep 2022 15:05:57 +0000 Received: from mail-pg1-x529.google.com ([2607:f8b0:4864:20::529]) by bombadil.infradead.org with esmtps (Exim 4.94.2 #2 (Red Hat Linux)) id 1odv6o-003lCA-QV for linux-nvme@lists.infradead.org; Thu, 29 Sep 2022 15:05:56 +0000 Received: by mail-pg1-x529.google.com with SMTP id 3so1716537pga.1 for ; Thu, 29 Sep 2022 08:05:53 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel-dk.20210112.gappssmtp.com; s=20210112; h=content-transfer-encoding:in-reply-to:from:references:cc:to :content-language:subject:user-agent:mime-version:date:message-id :from:to:cc:subject:date; bh=jgnDNASof/g3kUSSX5icXdxlDgaWwUplvsCMn1pF5vM=; b=JKBVyObYGRAOO4ywPCjymTsySSakqkGw4waL9JKUdqf0SMohmGWuMTTBmLcYp3jchM qVf6VGEwYD1B2crtpCBsCnbsJhVyMY1DFCc2n+BNyBIJg6inrzcPouCwkV3waR5XR0W/ rT3lA0gxdMhZKER49g29N1jEskq9SblBQTksO0Zb5ya6eQMq2L3nQGU+1a5Rg1aatI5A tYOpHtQ27ddm2/f0HOOUjWaG8K7ZYD4N8K00QzrXPLlpY5Id3khDKqI7MeHXCJStonUq Odsj0OmORM8Q3Q02Z2IaYLusLR7UNv0cuOHNFHgKT4VMfFuz/vcN4JN+1sNO1OReNkav tivg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=content-transfer-encoding:in-reply-to:from:references:cc:to :content-language:subject:user-agent:mime-version:date:message-id :x-gm-message-state:from:to:cc:subject:date; bh=jgnDNASof/g3kUSSX5icXdxlDgaWwUplvsCMn1pF5vM=; b=brHJbG2s40FIjUwpH/5F56XRKo2DfgLtbxGhfqgsf+FHsiZTg5Qx/fYbAC0NsNANX/ gx2fQTXkAOcFTKQE1HsyQyhiTlRRPLZKJDOgturQyaNgAZlG6wfc57QA9wYzXpZSaGfk 7uLAmtBEyWEv7tdAcciLmoRPG8qf3Mvffzhco6Ipm7cQ01cdEglNd4DuL1LAOr0YYauA 482SYAFDXld7/Wrz+BsRBaoiTFGFINmx9oBwq9LMJfb6XKyiAfrpB4Zh5rpbOkj4rxIO I+sHOCZeVwtDQEyEp65Q9nnzx1uM4EirovhXHJk1/fN1Mwo5Ef27hHyMDOqRi3kowP/i kzSg== X-Gm-Message-State: ACrzQf0ntzMAOcUZs7YycOIiFHW2uhTBCw9QvFbXPYIzRxINx5tOvzb6 OCo1NcNCLXLKTekHgbZ4iY5pPQ== X-Google-Smtp-Source: AMsMyM41XNEMrU48oiar1bH4MmONyZw4Yx23PNT3LPamAbK93khCZlOEW5+ehLdXeXaxwJbhGqnvYA== X-Received: by 2002:a63:590a:0:b0:439:6e0c:6381 with SMTP id n10-20020a63590a000000b004396e0c6381mr3317699pgb.141.1664463953462; Thu, 29 Sep 2022 08:05:53 -0700 (PDT) Received: from [192.168.1.136] ([198.8.77.157]) by smtp.gmail.com with ESMTPSA id u2-20020a170902bf4200b00178b6ccc8a0sm6027002pls.51.2022.09.29.08.05.52 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Thu, 29 Sep 2022 08:05:53 -0700 (PDT) Message-ID: <04b39974-6b55-7aca-70de-4a567f2eac8f@kernel.dk> Date: Thu, 29 Sep 2022 09:05:51 -0600 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux aarch64; rv:102.0) Gecko/20100101 Thunderbird/102.3.0 Subject: Re: [PATCH rfc] nvme: support io stats on the mpath device Content-Language: en-US To: Sagi Grimberg , Max Gurtovoy , linux-nvme@lists.infradead.org Cc: Christoph Hellwig , Keith Busch , Chaitanya Kulkarni , linux-block@vger.kernel.org, Hannes Reinecke References: <20220928195510.165062-1-sagi@grimberg.me> <20220928195510.165062-2-sagi@grimberg.me> <760a7129-945c-35fa-6bd6-aa315d717bc5@nvidia.com> From: Jens Axboe In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20220929_080554_883475_305A141C X-CRM114-Status: GOOD ( 11.14 ) X-BeenThere: linux-nvme@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "Linux-nvme" Errors-To: linux-nvme-bounces+linux-nvme=archiver.kernel.org@lists.infradead.org On 9/29/22 3:59 AM, Sagi Grimberg wrote: >> 3. Do you have some performance numbers (we're touching the fast path here) ? > > This is pretty light-weight, accounting is per-cpu and only wrapped by > preemption disable. This is a very small price to pay for what we gain. Is it? Enabling IO stats for normal devices has a very noticeable impact on performance at the higher end of the scale. So much so that I've contemplated how we can make this less expensive than it currently is. -- Jens Axboe