On Mon, Dec 17, 2012 at 01:33:14PM -0800, Tejun Heo wrote: > Hello, > > On Mon, Dec 17, 2012 at 04:27:36PM -0500, Vivek Goyal wrote: > > What I do care about is atleast being able to read and understand the > > code easily. Right now, it is hard to understand. I am still struggling > > to wrap my head around it. > > Hmm... I thought it was really simple. Maybe I'm just too familiar > with it. You just walk up the tree multiplying the fraction you have > at each level. It really doesn't get much simpler than that. > > > For example, while adding a group to service tree we calculate > > cfqg->vfaction as follows. > > > > vfr = vfr * pos->leaf_weight / pos->level_weight; > > > > and then > > > > vfr = vfr * pos->weight / parent->level_weight; > > > > cfqg->vfraction = max_t(unsigned, vfr, 1) > > > > If cfqg->vfraction is about cfqg then why should we take into account > > leaf_weight and level_weight. We should be just worried about pos->weight > > and parent->level_weight and that should determine vfaction of cfqg. > > Eh? Then how would it compete with the children cfqgs? You can > consider it as the hidden leaf node competing with the children cfqgs, > right? So, you take the leaf weight and divide it by the total active > weight of all the children (including the hidden leaf node). It isn't > different from the rest of the calculation. It just looks different > because leaf_weight is stored elsewhere and we look down there and > then walke up. The calculation being done is exactly the same one. Again it is coming from multiplexing cfqg and cfqg->task_group. So effectively we are calculating the vfraction of task_group inside cfqg. Once you say cfqg->vfraction, I immediately think of total share of group (including task_group and all children cgroups). May be cfqg->task_group_vfraction (or cfqg->tg_fraction) is a better name. Also descrition says. /* vfraction the fraction of vdisktime that a cfqg is entitled to */ May be we can clarify it that it is share of task_group of cfqg. I guess i am too familiar with how cpu has done it. I think I am getting confused with properties which belong to cfqg and properties which belong to cfqg->task_group. I guess if we prefix fields belong to task_group with somete suitable string, it might become little easier to understand. Thanks Vivek _______________________________________________ Containers mailing list Containers@xxxxxxxxxxxxxxxxxxxxxxxxxx https://lists.linuxfoundation.org/mailman/listinfo/containers
