Messages in this thread | | | Subject | Re: [PATCH v6 1/3] perf/core: use rb trees for pinned/flexible groups | From | Alexey Budankov <> | Date | Wed, 30 Aug 2017 11:30:26 +0300 |
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On 29.08.2017 16:51, Alexander Shishkin wrote: > Alexey Budankov <alexey.budankov@linux.intel.com> writes: > >> Now I figured that not all indexed events are always located under >> the root with the same cpu, and it depends on the order of insertion >> e.g. with insertion order 01,02,03,14,15,16 we get this: >> >> 02 >> / \ >> 01 14 >> / \ >> 03 15 >> \ >> 16 >> >> and it is unclear how to iterate cpu==0 part of tree in this case. > > Using this example, rb_next() should take you through the nodes in this > order (assuming you start with 01): 01, 02, 03, 14, etc. So you iterate > while event->cpu==cpu using rb_next() and you should be fine.
Well, indeed we get the most left leaf (03) in rb_next() for the case above.
> >> Iterating cpu specific subtree like this: >> >> #define for_each_group_event(event, group, cpu, pmu, field) \ >> for (event = rb_entry_safe(group_first(group, cpu, pmu), \ >> typeof(*event), field); \ >> event && event->cpu == cpu && event->pmu == pmu; \ >> event = rb_entry_safe(rb_next(&event->field), \ >> typeof(*event), field)) > > Afaict, this assumes that you are also ordering on event->pmu, which > should be reflected in your _less function. And also assuming that > group_first() is doing the right thing. Can we see the code?
I didn't do ordering by PMU for this patch set. Yet more I implemented groups_first() like this:
static struct perf_event * perf_event_groups_first(struct perf_event_groups *groups, int cpu) { struct perf_event *node_event = NULL; struct rb_node *node = NULL;
node = groups->tree.rb_node;
while (node) { node_event = container_of(node, struct perf_event, group_node);
if (cpu < node_event->cpu) { node = node->rb_left; } else if (cpu > node_event->cpu) { node = node->rb_right; } else { node = node->rb_left; } }
return node_event; }
and it doesn't work as expected for case above with cpu == 1.
I corrected the code above to this:
static struct perf_event * perf_event_groups_first(struct perf_event_groups *groups, int cpu) { struct perf_event *node_event = NULL, *match = NULL; struct rb_node *node = NULL;
node = groups->tree.rb_node;
while (node) { node_event = container_of(node, struct perf_event, group_node);
if (cpu < node_event->cpu) { node = node->rb_left; } else if (cpu > node_event->cpu) { node = node->rb_right; } else { match = node_event; node = node->rb_left; } }
return match; }
but now struggling with silent oopses which I guess are not related to multiplexing at all.
Please look at v8 for a while. It addresses your comments for v7.
> > Regards, > -- > Alex >
Thanks, Alexey
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