Messages in this thread | | | Date | Wed, 12 Dec 2012 15:29:55 +0800 | Subject | Re: performance drop after using blkcg | From | Zhao Shuai <> |
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2012/12/11 Vivek Goyal <vgoyal@redhat.com>: > These results are with slice_idle=0?
Yes, slice_idle is disabled.
> What's the storage you are using. Looking at the speed of IO I would > guess it is not one of those rotational disks.
I have done the same test on 3 different type of boxes,and all of them show a performance drop(30%-40%) after using blkcg. Though they have different type of disk, all the storage they use are traditional rotational devices(e.g."HP EG0146FAWHU", "IBM-ESXS").
> So if somebody wants to experiment, just tweak the code a bit to allow > preemption when a queue which lost share gets backlogged and you > practially have a prototype of iops based group scheduling.
Could you please explain more on this? How to adjust the code? I have test the following code piece, the result is we lost group differentiation.
cfq_group_served() { if (iops_mode(cfqd)) charge = cfqq->slice_dispatch; cfqg->vdisktime += cfq_scale_slice(charge, cfqg); }
-- Regards, Zhao Shuai
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