From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753500AbdKMP5v (ORCPT ); Mon, 13 Nov 2017 10:57:51 -0500 Received: from mail-qt0-f180.google.com ([209.85.216.180]:49930 "EHLO mail-qt0-f180.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753407AbdKMP5t (ORCPT ); Mon, 13 Nov 2017 10:57:49 -0500 X-Google-Smtp-Source: AGs4zMZuUOAkEKUvhd/6Moir3ko2xmWVl/EAfljeZNv2nFlEo9HvDq8pOGM1/0d2gnb7VprWiKXNyA== Date: Mon, 13 Nov 2017 07:57:45 -0800 From: Tejun Heo To: Shaohua Li Cc: axboe@kernel.dk, linux-kernel@vger.kernel.org, kernel-team@fb.com, lizefan@huawei.com, hannes@cmpxchg.org, cgroups@vger.kernel.org, guro@fb.com Subject: Re: [PATCH 7/7] blk-throtl: don't throttle the same IO multiple times Message-ID: <20171113155745.GI983427@devbig577.frc2.facebook.com> References: <20171112222613.3613362-1-tj@kernel.org> <20171112222613.3613362-8-tj@kernel.org> <20171113040716.kaheegc4qub42n6z@kernel.org> <20171113111348.GF983427@devbig577.frc2.facebook.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20171113111348.GF983427@devbig577.frc2.facebook.com> User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hello, On Mon, Nov 13, 2017 at 03:13:48AM -0800, Tejun Heo wrote: > You're right. If we wanna take this approach, we need to keep the > throttled flag while cloning. The clearing part is still correct tho. > Without that, I get 1/4 bw limit enforced. Hmm... I'm not quite sure > where that 1/4 is coming from tho. Will investigate more. Okay, this is because when we spiit, the split bio is the first part which gets issued and then the orignal bio is wound forward and requeued. So, for the splits, the original bio is the one which gets trimmed in the front and requeued, so not clearing BIO_THROTTLED is enough. I think we should still copy BIO_THROTTLED on clones so that we don't get suprises w/ other bio drivers. Thanks. -- tejun