From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-yw0-f194.google.com ([209.85.161.194]:36489 "EHLO mail-yw0-f194.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932436AbcKVV1S (ORCPT ); Tue, 22 Nov 2016 16:27:18 -0500 Date: Tue, 22 Nov 2016 16:27:15 -0500 From: Tejun Heo To: Shaohua Li Cc: linux-block@vger.kernel.org, linux-kernel@vger.kernel.org, Kernel-team@fb.com, axboe@fb.com, vgoyal@redhat.com Subject: Re: [PATCH V4 07/15] blk-throttle: make throtl_slice tunable Message-ID: <20161122212715.GD17534@htj.duckdns.org> References: <24137f881a149d30b98ef040367f26378128d4d2.1479161136.git.shli@fb.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii In-Reply-To: <24137f881a149d30b98ef040367f26378128d4d2.1479161136.git.shli@fb.com> Sender: linux-block-owner@vger.kernel.org List-Id: linux-block@vger.kernel.org Hello, On Mon, Nov 14, 2016 at 02:22:14PM -0800, Shaohua Li wrote: > throtl_slice is important for blk-throttling. A lot of stuffes depend on > it, for example, throughput measurement. It has 100ms default value, > which is not appropriate for all disks. For example, for SSD we might > use a smaller value to make the throughput smoother. This patch makes it > tunable. It bothers me a bit because time slice doesn't mean anything inherent to throttling. It really is an implementation detail - throttling can be implemented at per-operation level without time slice involved at all. It's okay to expose the knob if necessary but the meaning of the knob is almost completely arbitrary to users (as it has no inherent meaning). Thanks. -- tejun