Hi Vivek, Vivek Goyal <vgoyal@xxxxxxxxxx> wrote: > Ok. Our numbers can vary a bit depending on fio settings like block size > and underlying storage also. But that's not the important thing. Currently > with this test I just wanted to point out that model of ioprio with-in group > is currently broken with dm-ioband and good that you can reproduce that. > > One minor nit, for max latency you need to look at "clat " row and "max=" field > in fio output. Most of the time "max latency" will matter most. You seem to > be currently grepping for "maxt" which is just seems to be telling how > long did test run and in this case 30 seconds. > > Assigning reads to right context in CFQ and not to dm-ioband thread might > help a bit, but I am bit skeptical and following is the reason. > > CFQ relies on time providing longer time slice length for higher priority > process and if one does not use time slice, it looses its share. So the moment > you buffer even single bio of a process in dm-layer, if CFQ was servicing that > process at same time, that process will loose its share. CFQ will at max > anticipate for 8 ms and if buffering is longer than 8ms, CFQ will expire the > queue and move on to next queue. Later if you submit same bio and with > dm-ioband helper thread and even if CFQ attributes it to right process, it is > not going to help much as process already lost it slice and now a new slice > will start. O.K. I would like to figure something out this issue. > > > > Be that as it way, I think that if every bio can point the iocontext > > > > of the process, then it makes it possible to handle IO priority in the > > > > higher level controller. A patchse has already posted by Takhashi-san. > > > > What do you think about this idea? > > > > > > > > Date Tue, 22 Apr 2008 22:51:31 +0900 (JST) > > > > Subject [RFC][PATCH 1/10] I/O context inheritance > > > > From Hirokazu Takahashi <> > > > > http://lkml.org/lkml/2008/4/22/195 > > > > > > So far you have been denying that there are issues with ioprio with-in > > > group in higher level controller. Here you seems to be saying that there are > > > issues with ioprio and we need to take this patch in to solve the issue? I am > > > confused? > > > > The true intention of this patch is to preserve the io-context of a > > process which originate it, but I think that we could also make use of > > this patch for one of the way to solve this issue. > > > > Ok. Did you run the same test with this patch applied and how do numbers look > like? Can you please forward port it to 2.6.31 and I will also like to > play with it? I'm sorry, I have no time to do that this week. I would like to do the forward porting and test with it by the mini-summit when poissible. > I am running more tests/numbers with 2.6.31 for all the IO controllers and > planning to post it to lkml before we meet for IO mini summit. Numbers can > help us understand the issue better. > > In first phase I am planning to post numbers for IO scheudler controller > and dm-ioband. Then will get to max bw controller of Andrea Righi. That sounds good. Thank you for your work. > > I created those patches against 2.6.32-rc1 and made sure the patches > > can be cleanly applied to that version. > > I am applying dm-ioband patch first and then bio cgroup patches. Is this > right order? Will try again. Yes, the order is right. Here are the sha1sums. 9f4e50878d77922c84a29be9913a8b5c3f66e6ec linux-2.6.32-rc1.tar.bz2 15d7cc9d801805327204296a2454d6c5346dd2ae dm-ioband-1.14.0.patch 5e0626c14a40c319fb79f2f78378d2de5cc97b02 blkio-cgroup-v13.tar.bz2 Thanks, Ryo Tsuruta -- dm-devel mailing list dm-devel@xxxxxxxxxx https://www.redhat.com/mailman/listinfo/dm-devel
