Messages in this thread | | | Date | Mon, 28 Jan 2013 18:03:16 -0800 (PST) | From | Hugh Dickins <> | Subject | Re: [PATCH 6/11] ksm: remove old stable nodes more thoroughly |
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On Mon, 28 Jan 2013, Andrew Morton wrote: > On Fri, 25 Jan 2013 18:01:59 -0800 (PST) > Hugh Dickins <hughd@google.com> wrote: > > > +static int remove_all_stable_nodes(void) > > +{ > > + struct stable_node *stable_node; > > + int nid; > > + int err = 0; > > + > > + for (nid = 0; nid < nr_node_ids; nid++) { > > + while (root_stable_tree[nid].rb_node) { > > + stable_node = rb_entry(root_stable_tree[nid].rb_node, > > + struct stable_node, node); > > + if (remove_stable_node(stable_node)) { > > + err = -EBUSY; > > It's a bit rude to overwrite remove_stable_node()'s return value.
Well.... yes, but only the tiniest bit rude :)
> > > + break; /* proceed to next nid */ > > + } > > + cond_resched(); > > Why is this here?
Because we don't have a limit on the length of this loop, and if every node which remove_stable_node() finds is already stale, and has no rmap_item still attached, then there would be no rescheduling point in the unbounded loop without this one. I was taught to worry about bad latencies even in unpreemptible kernels.
Hugh
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