From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Subject: Re: [PATCH] cfq-iosched: fix the delay of cfq_group's vdisktime under iops mode To: Vivek Goyal References: <1488334064-34883-1-git-send-email-houtao1@huawei.com> <20170302102945.GA31792@quack2.suse.cz> <20170303195347.GC960@redhat.com> CC: Jan Kara , , , , From: Hou Tao Message-ID: Date: Mon, 6 Mar 2017 16:55:25 +0800 MIME-Version: 1.0 In-Reply-To: <20170303195347.GC960@redhat.com> Content-Type: text/plain; charset="windows-1252" List-ID: Hi Vivek, On 2017/3/4 3:53, Vivek Goyal wrote: > On Fri, Mar 03, 2017 at 09:20:44PM +0800, Hou Tao wrote: > > [..] >>> Frankly, vdisktime is in fixed-point precision shifted by >>> CFQ_SERVICE_SHIFT so using CFQ_IDLE_DELAY does not make much sense in any >>> case and just adding 1 to maximum vdisktime should be fine in all the >>> cases. But that would require more testing whether I did not miss anything >>> subtle. > > I think even 1 will work. But in the beginning IIRC I took the idea > from cpu scheduler. Adding a value bigger than 1 will allow you to add > some other group later before this group. (If you want to give that group > higher priority). I still don't understand why using a value bigger than 1 will allow a later added group to have a vdisktime less than the firstly added group. Could you explain it in more detail ? Regards, Tao > Thanks > Vivek > > . >