Messages in this thread | | | Date | Mon, 28 Mar 2011 09:17:05 -0400 | From | Vivek Goyal <> | Subject | Re: [PATCH 0/3] cfq-iosched: Fair cross-group preemption |
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On Fri, Mar 25, 2011 at 04:53:13PM -0700, Chad Talbott wrote: > On Fri, Mar 25, 2011 at 2:32 PM, Vivek Goyal <vgoyal@redhat.com> wrote: > >> You seem pretty unenthusiastic about a). How do you feel about b)? > > > > IMHO, Using RT group with throttling avoids introducing asymmetry between > > task and group attributes. So I will prefer that approch. Though it means > > more code as we will be introducing RT groups but that might be useful > > in general for something else too. (I am assuming that somebody makes > > use of RT class for cfqq). > > > > The one more down side of trying to use throttling is that one needs to > > come up with absolute limit. So one shall have to know disk capacity > > and if there are no BE tasks running then latency sensitive task will > > be unnecessarily throttled (until and unless some management software > > can monitor it and change limit dynamically). > > > > So if you are worried about setting the absolute limit part, then I guess > > I am fine with option a). But if you think that setting absolute limit > > is not a problem, then option b) is preferred. > > I prefer option a) - so much so that even with the older CFQ group > implementation we did work to merge the RT and BE service trees to > achieve that behavior. But I see that using blkio.class is a poor > choice of interface name. I will rename the interface and resubmit > the patch series (also with Gui's suggestion to keep the "_device" > suffix for consistency).
Do you need this feature to be global or per device or both?
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