From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S933888AbaE3PvQ (ORCPT ); Fri, 30 May 2014 11:51:16 -0400 Received: from mail-qg0-f47.google.com ([209.85.192.47]:55868 "EHLO mail-qg0-f47.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S933502AbaE3PvJ (ORCPT ); Fri, 30 May 2014 11:51:09 -0400 Date: Fri, 30 May 2014 11:51:05 -0400 From: Tejun Heo To: Paolo Valente Cc: Jens Axboe , Li Zefan , Fabio Checconi , Arianna Avanzini , Paolo Valente , linux-kernel@vger.kernel.org, containers@lists.linux-foundation.org, cgroups@vger.kernel.org Subject: Re: [PATCH RFC - TAKE TWO - 12/12] block, bfq: boost the throughput with random I/O on NCQ-capable HDDs Message-ID: <20140530155105.GF24871@htj.dyndns.org> References: <20140528221929.GG1419@htj.dyndns.org> <1401354343-5527-1-git-send-email-paolo.valente@unimore.it> <1401354343-5527-13-git-send-email-paolo.valente@unimore.it> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1401354343-5527-13-git-send-email-paolo.valente@unimore.it> User-Agent: Mutt/1.5.23 (2014-03-12) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, May 29, 2014 at 11:05:43AM +0200, Paolo Valente wrote: > This patch is basically the counterpart of patch 13 for NCQ-capable > rotational devices. Exactly as patch 13 does on flash-based devices > and for any workload, this patch disables device idling on rotational > devices, but only for random I/O. More precisely, idling is disabled > only for constantly-seeky queues (see patch 7). In fact, only with > these queues disabling idling boosts the throughput on NCQ-capable > rotational devices. > > To not break service guarantees, idling is disabled for NCQ-enabled > rotational devices and constantly-seeky queues only when the same > symmetry conditions as in patch 13, plus an additional one, hold. The > additional condition is related to the fact that this patch disables > idling only for constantly-seeky queues. In fact, should idling be Wouldn't it make more sense to limit queue depth to one unless the workload can clearly benefit from allowing higher queue depth? And I really think it'd bring more clarity if we just concentrate on rotational devices. Thanks. -- tejun