On Fri, 11 Nov 2016, Joonsoo Kim wrote: > Hello, David. > > Maintaining acitve/free_slab counters looks so complex. And, I think > that we don't need to maintain these counters for faster slabinfo. > Key point is to remove iterating n->slabs_partial list. > > We can calculate active slab/object by following equation as you did in > this patch. > > active_slab(n) = n->num_slab - the number of free_slab > active_object(n) = n->num_slab * cachep->num - n->free_objects > > To get the number of free_slab, we need to iterate n->slabs_free list > but I guess it would be small enough. > > If you don't like to iterate n->slabs_free list in slabinfo, just > maintaining the number of slabs_free would be enough. > Hi Joonsoo, It's a good point, although I don't think the patch has overly complex logic to keep track of slab state. We don't prefer to do any iteration in get_slabinfo() since users can read /proc/slabinfo constantly; it's better to just settle the stats when slab state changes instead of repeating an expensive operation over and over if someone is running slabtop(1) or /proc/slabinfo is scraped regularly for stats. That said, I imagine there are more clever ways to arrive at the same answer, and you bring up a good point about maintaining a n->num_slabs and n->free_slabs rather than n->active_slabs and n->free_slabs. I don't feel strongly about either approach, but I think some improvement, such as what this patch provides, is needed to prevent how expensive simply reading /proc/slabinfo can be. -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>