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

[Kirill Korotaev <dev@sw.ru>]

>>>>+	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