Re: [PATCH v2 09/16] rcu/tree: Maintain separate array for vmalloc ptrs

Uladzislau Rezki
2020-06-18T17:25:15Z

> > + // Handle two first channels.
> > + for (i = 0; i < FREE_N_CHANNELS; i++) {
> > + for (; bkvhead[i]; bkvhead[i] = bnext) {
> > + bnext = bkvhead[i]->next;
> > + debug_rcu_bhead_unqueue(bkvhead[i]);
> > +
> > + rcu_lock_acquire(&rcu_callback_map);
> > + if (i == 0) { // kmalloc() / kfree().
> > + trace_rcu_invoke_kfree_bulk_callback(
> > + rcu_state.name, bkvhead[i]->nr_records,
> > + bkvhead[i]->records);
> > +
> > + kfree_bulk(bkvhead[i]->nr_records,
> > + bkvhead[i]->records);
> > + } else { // vmalloc() / vfree().
> > + for (j = 0; j < bkvhead[i]->nr_records; j++) {
> > + trace_rcu_invoke_kfree_callback(
> > + rcu_state.name,
> > + bkvhead[i]->records[j], 0);
> > +
> > + vfree(bkvhead[i]->records[j]);
> > + }
> > + }
> > + rcu_lock_release(&rcu_callback_map);
>
> Not an emergency, but did you look into replacing this "if" statement
> with an array of pointers to functions implementing the legs of the
> "if" statement? If nothing else, this would greatly reduced indentation.
>
>
> I am taking this as is, but if you have not already done so, could you
> please look into this for a follow-up patch?
>
I do not think it makes sense, because it would require to check each
pointer in the array, what can lead to many branching, i.e. "if-else"
instructions.

Paul, thank you to take it in!

--
Vlad Rezki