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 vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id C5A28C3DA7A for ; Thu, 5 Jan 2023 17:36:27 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S235280AbjAERgZ (ORCPT ); Thu, 5 Jan 2023 12:36:25 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:48724 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S235408AbjAERgE (ORCPT ); Thu, 5 Jan 2023 12:36:04 -0500 Received: from mail-pl1-x629.google.com (mail-pl1-x629.google.com [IPv6:2607:f8b0:4864:20::629]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 8A3C3BC87; Thu, 5 Jan 2023 09:36:02 -0800 (PST) Received: by mail-pl1-x629.google.com with SMTP id p24so17532234plw.11; Thu, 05 Jan 2023 09:36:02 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20210112; h=in-reply-to:content-transfer-encoding:content-disposition :mime-version:references:message-id:subject:cc:to:from:date:sender :from:to:cc:subject:date:message-id:reply-to; bh=gkjsNq+41nhz5t6YNHufJptj0TXGHPydjE1ADy7+6FM=; b=F7AETA8YmQngoALJiwWtbL0ff8RtVbY4EEr53C6FVlL+DjvgCS7aideTdCWmxjFESd SeiRq631vXOAX++cF5PyZgvg1K66m5yYZ1/kNZWXsC6IwAeKeSZd5dJI25JEOakb5hTn koOxsxdTnhPtdbZa50u70QRWGBbgPhkudNr+UVeZO49V+rJahQKqkZ1pZR+sqjplBze3 q35Wqugk6MwBc7S+ubvDZFqhYjXGVsB/XPQOU15imjrES3mE+4jS6D5EO6hub0FHZxAT +zCaPPlxhFluLFItLj3F5QdevNoFUcoaXuo+CM0bND1qvelEblmhqLuD8fraDS1YHsIn MT+g== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=in-reply-to:content-transfer-encoding:content-disposition :mime-version:references:message-id:subject:cc:to:from:date:sender :x-gm-message-state:from:to:cc:subject:date:message-id:reply-to; bh=gkjsNq+41nhz5t6YNHufJptj0TXGHPydjE1ADy7+6FM=; b=p5e2ZMMoptC1P2yTbIajKKg4yBAKQL0trXTiN8O3nAcR3IttqcE7EBNDrBqJG8pRSC MzUzQUSdwWa+E9J2tZE9DhPMOrn0r20wq6vWSIcbrizoN0A5HTDJVSkQls07Q/jdj690 a046HU1Ce4w5NS7j712wX1DZBgplC8yXXPjxkwCmUmvTDK1fPRL0UkVC2PbSjiLP1N63 ExSaEbzLX+MoTZEfooswVkVl6ofiq8q1mtGOAbCFK4NMju34vnEDO88lDmjg7qdz+Uac nzRnGs0jF1TgwVWuLRPVXJAhYU24FFw66mFT9F8FL+UD/SAGPzdXNnGGqvw9lZeK8zND iRAw== X-Gm-Message-State: AFqh2kqdDKJP09Xqx9r7rpuWoLvsByQA+9t1/fJl1DP/SYaCrbsFPjOc jya8L+A5m9bprZyxzbpZrlwL/mCI7Fs= X-Google-Smtp-Source: AMrXdXsYDWP5shGMiAXXVQkIfz7JzRr2YwOxVFcN+ZqNqk6WEmOWE6UE2GTNjP8E23+8A9XtfuGZfQ== X-Received: by 2002:a17:90a:f309:b0:219:9e19:8259 with SMTP id ca9-20020a17090af30900b002199e198259mr55174897pjb.46.1672940161933; Thu, 05 Jan 2023 09:36:01 -0800 (PST) Received: from localhost (2603-800c-1a02-1bae-a7fa-157f-969a-4cde.res6.spectrum.com. [2603:800c:1a02:1bae:a7fa:157f:969a:4cde]) by smtp.gmail.com with ESMTPSA id mz4-20020a17090b378400b0020aacde1964sm1623674pjb.32.2023.01.05.09.36.01 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 05 Jan 2023 09:36:01 -0800 (PST) Sender: Tejun Heo Date: Thu, 5 Jan 2023 07:35:59 -1000 From: Tejun Heo To: Michal =?iso-8859-1?Q?Koutn=FD?= Cc: Jinke Han , josef@toxicpanda.com, axboe@kernel.dk, cgroups@vger.kernel.org, linux-block@vger.kernel.org, linux-kernel@vger.kernel.org, yinxin.x@bytedance.com, jack@suse.cz Subject: Re: [PATCH v3] blk-throtl: Introduce sync and async queues for blk-throtl Message-ID: References: <20221226130505.7186-1-hanjinke.666@bytedance.com> <20230105161854.GA1259@blackbody.suse.cz> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <20230105161854.GA1259@blackbody.suse.cz> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hello, On Thu, Jan 05, 2023 at 05:18:54PM +0100, Michal Koutný wrote: > I guess similar problem would arise for devices that are "naturally" > slow. > Then: > a) it must have been solved elsewhere in the block layer (but it's > broken), > b) it should be solved generically in the block layer (thus this is only > a partial solution). Hard limits tend to make this sort of problems a lot more pronounced because the existing mechanisms tend to break down for the users which are severely throttled down even while the device as a whole is fairly idle. cpu.max often triggers severe priority inversions too, so it isn't too surprising that people hit severe priority inversion issues w/ io.max. Another problem with blk-throttle is that it doesn't prioritize shared IOs identified by bio_issue_as_root_blkg() like iolatency and iocost do, so there can be very severe priority inversions when e.g. journal commit gets trapped in a low priority cgroup further exacerbating issues like this. Thanks. -- tejun