Re: [ckrm-tech] [RFC][PATCH 2/7] UBC: core (structures, API)

[Kirill Korotaev]

> > > > +	for (p = ub; p != NULL; p = p->parent) {
> > >
> > >
> > > Seems rather expensive to walk up the tree for every charge. Especially
> > > if the administrator wants a fine degree of resource control and makes a
> > > tall tree. This would be a problem especially when it comes to resources
> > > that require frequent and fast allocation.
> >
> > in heirarchical accounting you always have to update all the nodes :/
> > with flat UBC this doesn't introduce significant overhead.
>
>
> Except that you eventually have to lock ub0. Seems that the cache line
> for that spinlock could bounce quite a bit in such a hot path.
do you mean by ub0 host system ub which we call ub0
or you mean a top ub?

> Chandra, doesn't Resource Groups avoid walking more than 1 level up the
> hierarchy in the "charge" paths?

Kirill

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