On Fri, Nov 11, 2016 at 02:30:39AM -0800, David Rientjes wrote: > 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.
Hello, Sorry for long delay. I agree that this improvement is needed. Could you try the approach that maintains n->num_slabs and n->free_slabs? I guess that it would be simpler than this patch so more maintainable. Thanks.
