Messages in this thread | | | Date | Thu, 03 Dec 2009 16:41:50 +0800 | From | Gui Jianfeng <> | Subject | Re: Block IO Controller V4 |
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Vivek Goyal wrote: > On Wed, Dec 02, 2009 at 09:51:36AM +0800, Gui Jianfeng wrote: >> Vivek Goyal wrote: >>> Hi Jens, >>> >>> This is V4 of the Block IO controller patches on top of "for-2.6.33" branch >>> of block tree. >>> >>> A consolidated patch can be found here: >>> >>> http://people.redhat.com/vgoyal/io-controller/blkio-controller/blkio-controller-v4.patch >>> >> Hi Vivek, >> >> It seems this version doesn't work very well for "direct(O_DIRECT) sequence read" mode. >> For example, you can create group A and group B, then assign weight 100 to group A and >> weight 400 to group B, and you run "direct sequence read" workload in group A and B >> simultaneously. Ideally, we should see 1:4 disk time differentiation for group A and B. >> But actually, I see almost 1:2 disk time differentiation for group A and B. I'm looking >> into this issue. >> BTW, V3 works well for this case. > > Hi Gui, > > In my testing of 8 fio jobs in 8 cgroups, direct sequential reads seems to > be working fine. > > http://lkml.org/lkml/2009/12/1/367 > > I suspect that in some case we choose not to idle on the group and it gets > deleted from service tree hence we loose share. Can you have a look at > blkio.dequeue files. If there are excessive deletions, that will signify > that we are loosing share because we chose not to idle. > > If yes, please also run blktrace to see in what cases we chose not to > idle. > > In V3, I had a stronger check to idle on the group if it is empty using > wait_busy() function. In V4 I have removed that and trying to wait busy > on a queue by extending its slice if it has consumed its allocated slice.
Hi Vivek,
I ckecked the blktrace output, it seems that io group was deleted all the time, because we don't have group idle any more. I pulled the wait_busy code back to V4, and retest it, problem seems disappeared.
So i suggest that we need to retain the wait_busy code.
Thanks, Gui
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