From: Rik van Riel Subject: Re: [PATCH 11/23] io-controller: Introduce group idling Date: Sat, 29 Aug 2009 20:38:20 -0400 Message-ID: <4A99C9FC.2010004@redhat.com> References: <1251495072-7780-1-git-send-email-vgoyal@redhat.com> <1251495072-7780-12-git-send-email-vgoyal@redhat.com> Reply-To: device-mapper development Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <1251495072-7780-12-git-send-email-vgoyal@redhat.com> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: dm-devel-bounces@redhat.com Errors-To: dm-devel-bounces@redhat.com To: Vivek Goyal Cc: dhaval@linux.vnet.ibm.com, peterz@infradead.org, dm-devel@redhat.com, dpshah@google.com, jens.axboe@oracle.com, agk@redhat.com, balbir@linux.vnet.ibm.com, paolo.valente@unimore.it, jmarchan@redhat.com, guijianfeng@cn.fujitsu.com, fernando@oss.ntt.co.jp, mikew@google.com, jmoyer@redhat.com, nauman@google.com, mingo@elte.hu, m-ikeda@ds.jp.nec.com, lizf@cn.fujitsu.com, fchecconi@gmail.com, s-uchida@ap.jp.nec.com, containers@lists.linux-foundation.org, linux-kernel@vger.kernel.org, akpm@linux-foundation.org, righi.andrea@gmail.com, torvalds@linux-foundation.org List-Id: dm-devel.ids Vivek Goyal wrote: > o It is not always that IO from a process or group is continuous. There are > cases of dependent reads where next read is not issued till previous read > has finished. For such cases, CFQ introduced the notion of slice_idle, > where we idle on the queue for sometime hoping next request will come > and that's how fairness is provided otherwise queue will be deleted > immediately from the service tree and this process will not get the > fair share. > > o This patch introduces the similar concept at group level. Idle on the group > for a period of "group_idle" which is tunable through sysfs interface. So > if a group is empty and about to be deleted, we idle for the next request. > > o This patch also introduces the notion of wait busy where we wait for one > extra group_idle period even if queue has consumed its time slice. The > reason being that group will loose its share upon removal from service > tree as some other entity will be picked for dispatch and vtime jump will > take place. > > Signed-off-by: Vivek Goyal Acked-by: Rik van Riel -- All rights reversed.