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=-2.2 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, 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 5F201C2D0C5 for ; Thu, 12 Dec 2019 01:41:49 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 350082464B for ; Thu, 12 Dec 2019 01:41:49 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=kernel-dk.20150623.gappssmtp.com header.i=@kernel-dk.20150623.gappssmtp.com header.b="hrnF4TXg" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727527AbfLLBls (ORCPT ); Wed, 11 Dec 2019 20:41:48 -0500 Received: from mail-pf1-f195.google.com ([209.85.210.195]:40542 "EHLO mail-pf1-f195.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727473AbfLLBls (ORCPT ); Wed, 11 Dec 2019 20:41:48 -0500 Received: by mail-pf1-f195.google.com with SMTP id q8so229199pfh.7 for ; Wed, 11 Dec 2019 17:41:47 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel-dk.20150623.gappssmtp.com; s=20150623; h=subject:from:to:cc:references:message-id:date:user-agent :mime-version:in-reply-to:content-language:content-transfer-encoding; bh=QxnRj1KTspHy7p7jjV7BEiC8kTXAQbaB4Nasa0uBmKs=; b=hrnF4TXgpHDXedLBaY8w522NQV3GgLZp7239lwIiy9APNQKtr7vpyOoUxgMf4c4pPn zgSquxRTfw5cwSdsjtl6c6fDxnYOqeV4fmJ2Gldio+OHoocZY7Z/6hI0wy5a4O1jgRgO iF1mSK0vpjSK1cI9IOA9ZpTOkJuyLyobGk/k1zVU/7TDgIyO9KQeAfMdBp+LcnoXK0X+ J/9TA64kcKSg8Jsvji+Y/wugIAHOqXrh4bk5/Rbcu5uexhTu3drPECCqLYk1+JtsYpgl NbPkRosZagw/jIkQr2JhkyH//XXiiGFB1d6UleMnNPhFgQ8z2rynbwm2S6DXqiySojOu QI7g== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:subject:from:to:cc:references:message-id:date :user-agent:mime-version:in-reply-to:content-language :content-transfer-encoding; bh=QxnRj1KTspHy7p7jjV7BEiC8kTXAQbaB4Nasa0uBmKs=; b=nAXzMY3ARlOSQj6M7+kmWC4PGjXGg5e0dlAvA5qHFvwZeF+VAKreRLtkiNioTpUYBO gkJAPePPw8Z4VX/FPWLq4psBSqEfPH7GQE4jYQfhj2mzHrII8htkBeo1pulX99HbttW/ okK7/w0tVISzBxDftfsjeIFJ1tCcW2XqgDhr5O2qbDO5SZi98D6WvH+Pb+wNxIwhqVh5 +zlhhzsZ0Y2C4eUMVQIWsm9EW07NDAYavck0xbjUiZ+O0Z4RseAKIkklSqT974ERSIv8 vIAYsYOs8szqY5TYKqkX4+0wJTZeBN08DFPUmRVxLhYpQz8dhyPBSAmABj2F87Fugomz L4Rg== X-Gm-Message-State: APjAAAXUbqDAEUbz/slWrr1MsDJK3uUr1zotSjR+5vmL1hJuSMr3qu66 agi3sy4yUB8a5AjBnuHdGobmDAd98J5aMA== X-Google-Smtp-Source: APXvYqwUun2qLSYWDkJmEhhOuR/RBu3Dvqm+DjkY/o2GxGB0RxGae2HfaWEfH2qhUPN7GXt7FDDbyA== X-Received: by 2002:a65:4203:: with SMTP id c3mr7635957pgq.368.1576114907080; Wed, 11 Dec 2019 17:41:47 -0800 (PST) Received: from [192.168.1.188] ([66.219.217.145]) by smtp.gmail.com with ESMTPSA id v4sm3619850pjb.24.2019.12.11.17.41.45 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Wed, 11 Dec 2019 17:41:46 -0800 (PST) Subject: Re: [PATCHSET v3 0/5] Support for RWF_UNCACHED From: Jens Axboe To: Linus Torvalds Cc: Linux-MM , linux-fsdevel , linux-block , Matthew Wilcox , Chris Mason , Dave Chinner , Johannes Weiner References: <20191211152943.2933-1-axboe@kernel.dk> <0d4e3954-c467-30a7-5a8e-7c4180275533@kernel.dk> <1c93194a-ed91-c3aa-deb5-a3394805defb@kernel.dk> Message-ID: <6e2ca035-0e06-1def-5ea9-90a7466b2d49@kernel.dk> Date: Wed, 11 Dec 2019 18:41:44 -0700 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.2.2 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: linux-fsdevel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@vger.kernel.org On 12/11/19 6:29 PM, Jens Axboe wrote: > On 12/11/19 6:22 PM, Linus Torvalds wrote: >> On Wed, Dec 11, 2019 at 5:11 PM Jens Axboe wrote: >>> >>> 15K is likely too slow to really show an issue, I'm afraid. The 970 >>> is no slouch, but your crypt setup will likely hamper it a lot. You >>> don't have a non-encrypted partition on it? >> >> No. I normally don't need all that much disk, so I've never upgraded >> my ssd from the 512G size. >> >> Which means that it's actually half full or so, and I never felt like >> "I should keep an unencrypted partition for IO testing", since I don't >> generally _do_ any IO testing. >> >> I can get my load up with "numjobs=8" and get my iops up to the 100k >> range, though. >> >> But kswapd doesn't much seem to care, the CPU percentage actually does >> _down_ to 0.39% when I try that. Probably simply because now my CPU's >> are busy, so they are running at 4.7Ghz instead of the 800Mhz "mostly >> idle" state ... >> >> I guess I should be happy. It does mean that the situation you see >> isn't exactly the normal case. I understand why you want to do the >> non-cached case, but the case I think it the worrisome one is the >> regular buffered one, so that's what I'm testing (not even trying the >> noaccess patches). >> >> So from your report I went "uhhuh, that sounds like a bug". And it >> appears that it largely isn't - you're seeing it because of pushing >> the IO subsystem by another order of magnitude (and then I agree that >> "under those kinds of IO loads, caching just won't help") > > I'd very much argue that it IS a bug, maybe just doesn't show on your > system. My test box is a pretty standard 2 socket system, 24 cores / 48 > threads, 2 nodes. The last numbers I sent were 100K IOPS, so nothing > crazy, and granted that's only 10% kswapd cpu time, but that still seems > very high for those kinds of rates. I'm surprised you see essentially no > kswapd time for the same data rate. > > We'll keep poking here, I know Johannes is spending some time looking > into the reclaim side. Out of curiosity, just tried it on my laptop, which also has some samsung drive. Using 8 jobs, I get around 100K IOPS too, and this is my top listing: 23308 axboe 20 0 623156 1304 8 D 10.3 0.0 0:03.81 fio 23309 axboe 20 0 623160 1304 8 D 10.3 0.0 0:03.81 fio 23311 axboe 20 0 623168 1304 8 D 10.3 0.0 0:03.82 fio 23313 axboe 20 0 623176 1304 8 D 10.3 0.0 0:03.82 fio 23314 axboe 20 0 623180 1304 8 D 10.3 0.0 0:03.81 fio 162 root 20 0 0 0 0 S 9.9 0.0 0:12.97 kswapd0 23307 axboe 20 0 623152 1304 8 D 9.9 0.0 0:03.84 fio 23310 axboe 20 0 623164 1304 8 D 9.9 0.0 0:03.81 fio 23312 axboe 20 0 623172 1304 8 D 9.9 0.0 0:03.80 fio kswapd is between 9-11% the whole time, and the profile looks very similar to what I saw on my test box: 35.79% kswapd0 [kernel.vmlinux] [k] xas_create 9.97% kswapd0 [kernel.vmlinux] [k] free_pcppages_bulk 9.94% kswapd0 [kernel.vmlinux] [k] isolate_lru_pages 7.78% kswapd0 [kernel.vmlinux] [k] shrink_page_list 3.78% kswapd0 [kernel.vmlinux] [k] xas_clear_mark 3.08% kswapd0 [kernel.vmlinux] [k] workingset_eviction 2.48% kswapd0 [kernel.vmlinux] [k] __isolate_lru_page 2.06% kswapd0 [kernel.vmlinux] [k] page_mapping 1.95% kswapd0 [kernel.vmlinux] [k] __remove_mapping So now I'm even more puzzled why your (desktop?) doesn't show it, it must be more potent than my x1 laptop. But for me, the laptop and 2 socket test box show EXACTLY the same behavior, laptop is just too slow to make it really pathological. -- Jens Axboe