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 C347FC433EF for ; Mon, 16 May 2022 18:46:12 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1345136AbiEPSqL (ORCPT ); Mon, 16 May 2022 14:46:11 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:32962 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1345133AbiEPSqK (ORCPT ); Mon, 16 May 2022 14:46:10 -0400 Received: from mail-pl1-x62a.google.com (mail-pl1-x62a.google.com [IPv6:2607:f8b0:4864:20::62a]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 073293A5FB; Mon, 16 May 2022 11:46:10 -0700 (PDT) Received: by mail-pl1-x62a.google.com with SMTP id bh5so3492775plb.6; Mon, 16 May 2022 11:46:10 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20210112; h=sender:date:from:to:cc:subject:message-id:references:mime-version :content-disposition:in-reply-to; bh=Q2pjX9hOL1SP4Vyyi9JgJUjFRgviNJxEws7hy+EnHvM=; b=TPUV128Bqc8Lp2KlNU/4k8JVfaNRh0+SRpFtG0T6X0A9QO5TVp4wksjKTqH7qJ6h/k g+YJMm4YRFqQl+LkVWRS72LSVkfj9aXfmOpMfuNw++yDXk1fsjYjj4QGI7mnOrrAElTf SnWHqa9VfpEjZnF53BzrLrwftACFyUiS4CTTVbrFSL9ORVpVOGkbmwBv2Fh4LZU9loy9 K9CJVpKXNCtEWbGynmi+VwSdfZm/khWGaZIiudffG9srFSvqtiEpLO0ttob6kxdFCeRa iM5z9sS7tfEGqYjCtgrn3as5LS0V4tVzz6u/rap7DnhXl+P4k8oJRMFg+W/zkuljG2Tv c4oA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=x-gm-message-state:sender:date:from:to:cc:subject:message-id :references:mime-version:content-disposition:in-reply-to; bh=Q2pjX9hOL1SP4Vyyi9JgJUjFRgviNJxEws7hy+EnHvM=; b=TqhstzoZuzkILe2iod6ismWNNf8Ai06/fDXtW7cpYsKUDC3B1CsWopEKuUBstrN5ym N50ggMJVhtwypyBEX6xRVpKXu1yf+VzlctD0u6usLQi4qbe7iiVf/ML5wrNl7U1KGYSl 6WuVnxqzoqJvvP8Jq/Ww/TLiIrs/jPoLLjg9Tz79wtf/wUYErAuJj0zlUg1Ml+fdMoTt bQfzxTQmQ/TtgMYZqOfAw2I1gDK5fOQlZB9wN6PpMg6MrpGKE132PkKdKzlhma3nWS0U uYazCQ3/87NlbyvxyYBVxxWd+T22+KG545XVN5ipPmmBDhW+h5prFXqzw8kNnZZHN0O8 ISag== X-Gm-Message-State: AOAM5336HbAm2kMAKflKYIRHS4FZ5SX9rCW9YyWlQOtrmncpOrlrhKBc UC/uAiTNdWdeqV1aOOhUVZM= X-Google-Smtp-Source: ABdhPJxPyVOJDYm/TchnhmmiNYcjTqQOqSC+zIoIVkBIs2+L+IkTuhublfxsXjiZe5eLST+BoBB4eA== X-Received: by 2002:a17:902:ef45:b0:155:cede:5a9d with SMTP id e5-20020a170902ef4500b00155cede5a9dmr18737268plx.93.1652726769388; Mon, 16 May 2022 11:46:09 -0700 (PDT) Received: from localhost ([2620:10d:c090:400::4:62fc]) by smtp.gmail.com with ESMTPSA id 9-20020a170902c14900b0016168e90f2csm3454145plj.208.2022.05.16.11.46.08 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 16 May 2022 11:46:08 -0700 (PDT) Sender: Tejun Heo Date: Mon, 16 May 2022 08:46:07 -1000 From: Tejun Heo To: Chengming Zhou Cc: axboe@kernel.dk, linux-block@vger.kernel.org, linux-kernel@vger.kernel.org, duanxiongchun@bytedance.com, songmuchun@bytedance.com Subject: Re: [PATCH] blk-iocost: fix very large vtime when iocg activate Message-ID: References: <20220516084045.96004-1-zhouchengming@bytedance.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20220516084045.96004-1-zhouchengming@bytedance.com> Precedence: bulk List-ID: X-Mailing-List: linux-block@vger.kernel.org On Mon, May 16, 2022 at 04:40:45PM +0800, Chengming Zhou wrote: > When the first iocg activate after blk_iocost_init(), now->vnow > maybe smaller than ioc->margins.target, cause very large vtarget > since it's u64. > > vtarget = now->vnow - ioc->margins.target; > atomic64_add(vtarget - vtime, &iocg->vtime); > > Then the iocg's vtime will be very large too, larger than now->vnow. It's a wrapping counter. Please take a look at how time_before64() and friends work. Nacked-by: Tejun Heo Again, please spend more effort understanding the code before sending these subtle patches. Thanks. -- tejun