From patchwork Mon Nov 13 06:34:07 2017 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Paolo Valente X-Patchwork-Id: 10055175 Return-Path: Received: from mail.wl.linuxfoundation.org (pdx-wl-mail.web.codeaurora.org [172.30.200.125]) by pdx-korg-patchwork.web.codeaurora.org (Postfix) with ESMTP id 44A6A6029B for ; Mon, 13 Nov 2017 06:35:28 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id 3608028FB8 for ; Mon, 13 Nov 2017 06:35:28 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id 286A02908D; Mon, 13 Nov 2017 06:35:28 +0000 (UTC) X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on pdx-wl-mail.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-6.5 required=2.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,RCVD_IN_DNSWL_HI,RCVD_IN_SORBS_SPAM autolearn=unavailable version=3.3.1 Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id B598C28FB8 for ; Mon, 13 Nov 2017 06:35:27 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751863AbdKMGee (ORCPT ); Mon, 13 Nov 2017 01:34:34 -0500 Received: from mail-wm0-f68.google.com ([74.125.82.68]:53759 "EHLO mail-wm0-f68.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751485AbdKMGeb (ORCPT ); Mon, 13 Nov 2017 01:34:31 -0500 Received: by mail-wm0-f68.google.com with SMTP id g141so12739863wmg.2 for ; Sun, 12 Nov 2017 22:34:31 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linaro.org; s=google; h=from:to:cc:subject:date:message-id:in-reply-to:references; bh=0C09xARCq5lRGObZ7ietUdh2leD6jSM28GjTpi/l40E=; b=ZR+Jg9saLT8XW9jz8jxIz9lwIbKbX1DjVBVq1DBPcCKlkyiVI6PzrY9Cz+Pqpsr72e ny0yAWe2ZINLSMgh1s0uvxy5FihMNMr3N41yC41uwMRTPiERm88ZFA9IZ5xvbrGLwo7f lkSmBAeIwshVHFou0pa11o9VNSDM+YXbXENQo= X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:from:to:cc:subject:date:message-id:in-reply-to :references; bh=0C09xARCq5lRGObZ7ietUdh2leD6jSM28GjTpi/l40E=; b=a52ouNjAsQLlYzWlMC7wzmf22CLSWxxNoFhWKwh3PnHXqtK1Bn5yteMN8drFuuPnDL OkiXQx8nWpXDq25EdwVVoTTAskQgDyEFrgvOQLyfjJwgk2/45Rmhn7M/jI88SwMJDpUP t9UL1r0fbCG72xuRKY5OiSmvZzH0h2S1w4f+4nxfN5gtmW32PLlM0AWt6jhiyBCf1dWQ awDIIYTj0smQGBNFUCM+GL96HAGLfKR23I466DnY9N7a2Jgzeo0rnRx0vfvQgnWmQJCC 60vYq1cyC7HPT6+tXgiHhcf/3lV9f32XjBTwe3xzHQxQiW6rCQfi9PCCjl6ZLKsv5IMl Uz1Q== X-Gm-Message-State: AJaThX6yyK1kVJh7ueZbPPWjku8M1oDBT4FDA6INYmDRSQLmaERVai53 s/9fqpJKt8mTppFIQbZBOAFXTw== X-Google-Smtp-Source: AGs4zMZ6n1UTeewRwlzzFp4M98keuZJ974bO5zfpmDTdkNy5KZxkKJZoiVfClibBBl1nyUAZGLo84A== X-Received: by 10.28.6.6 with SMTP id 6mr5688560wmg.114.1510554870302; Sun, 12 Nov 2017 22:34:30 -0800 (PST) Received: from localhost.localdomain ([5.169.167.83]) by smtp.gmail.com with ESMTPSA id 10sm11158429wml.27.2017.11.12.22.34.28 (version=TLS1 cipher=AES128-SHA bits=128/128); Sun, 12 Nov 2017 22:34:29 -0800 (PST) From: Paolo Valente To: Jens Axboe Cc: linux-block@vger.kernel.org, linux-kernel@vger.kernel.org, ulf.hansson@linaro.org, broonie@kernel.org, linus.walleij@linaro.org, lee.tibbert@gmail.com, oleksandr@natalenko.name, lucmiccio@gmail.com, bfq-iosched@googlegroups.com, Paolo Valente Subject: [PATCH BUGFIX/IMPROVEMENT 1/4] doc, block, bfq: update max IOPS sustainable with BFQ Date: Mon, 13 Nov 2017 07:34:07 +0100 Message-Id: <20171113063410.3029-2-paolo.valente@linaro.org> X-Mailer: git-send-email 2.10.0 In-Reply-To: <20171113063410.3029-1-paolo.valente@linaro.org> References: <20171113063410.3029-1-paolo.valente@linaro.org> Sender: linux-block-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-block@vger.kernel.org X-Virus-Scanned: ClamAV using ClamSMTP We have investigated more deeply the performance of BFQ, in terms of number of IOPS that can be processed by the CPU when BFQ is used as I/O scheduler. In more detail, using the script [1], we have measured the number of IOPS reached on top of a null block device configured with zero latency, as a function of the workload (sequential read, sequential write, random read, random write) and of the system (we considered desktops, laptops and embedded systems). Basing on the resulting figures, with this commit we update the current, conservative IOPS range reported in BFQ documentation. In particular, the documentation now reports, for each of three different systems, the lowest number of IOPS obtained for that system with the above test (namely, the value obtained with the workload leading to the lowest IOPS). [1] https://github.com/Algodev-github/IOSpeed Reviewed-by: Lee Tibbert Signed-off-by: Paolo Valente Signed-off-by: Luca Miccio --- Documentation/block/bfq-iosched.txt | 17 +++++++++++------ 1 file changed, 11 insertions(+), 6 deletions(-) diff --git a/Documentation/block/bfq-iosched.txt b/Documentation/block/bfq-iosched.txt index 3d6951d..7a93615 100644 --- a/Documentation/block/bfq-iosched.txt +++ b/Documentation/block/bfq-iosched.txt @@ -20,12 +20,17 @@ for that device, by setting low_latency to 0. See Section 3 for details on how to configure BFQ for the desired tradeoff between latency and throughput, or on how to maximize throughput. -On average CPUs, the current version of BFQ can handle devices -performing at most ~30K IOPS; at most ~50 KIOPS on faster CPUs. As a -reference, 30-50 KIOPS correspond to very high bandwidths with -sequential I/O (e.g., 8-12 GB/s if I/O requests are 256 KB large), and -to 120-200 MB/s with 4KB random I/O. BFQ is currently being tested on -multi-queue devices too. +BFQ has a non-null overhead, which limits the maximum IOPS that the +CPU can process for a device scheduled with BFQ. To give an idea of +the limits on slow or average CPUs, here are BFQ limits for three +different CPUs, on, respectively, an average laptop, an old desktop, +and a cheap embedded system, in case full hierarchical support is +enabled (i.e., CONFIG_BFQ_GROUP_IOSCHED is set): +- Intel i7-4850HQ: 250 KIOPS +- AMD A8-3850: 170 KIOPS +- ARM CortexTM-A53 Octa-core: 45 KIOPS + +BFQ works for multi-queue devices too. The table of contents follow. Impatients can just jump to Section 3.