On 23.08.2017 16:39, Alexander Shishkin wrote:
> Alexey Budankov <alexey.budan...@linux.intel.com> writes:
>
>>>>>> bool event_less(left, right)
>>>>>> {
>>>>>> if (left->cpu < right->cpu)
>>>>>> return true;
>>>>>>
>>>>>> if (left->cpu > right_cpu)
>>>>>> return false;
>>>>>>
>>>>>> if (left->vtime < right->vtime)
>>>>>> return true;
>>>>>>
>>>>>> return false;
>>>>>> }
>>>>>>
>>>>>> insert_group(group, event, tail)
>>>>>> {
>>>>>> if (tail)
>>>>>> event->vtime = ++group->vtime;
>>>>>>
>>>>>> tree_insert(&group->root, event);
>>>>>> }
>
> [ ... ]
>
>> 2. implementing special _less() function and rotation by re-inserting
>> group with incremented index;
>>
>
> [ ... ]
>
>> 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
>
> How did you arrive at this? Seeing the actual code would help, because
> this is not the ordering we're looking for. With Peter's earlier example
> (quoted above) it shouldn't look like this.
I implemented the solution Peter suggested. Then I was testing and noticed
considerable difference in amount of collected samples when multiplexing
event, in comparison to the version with tree of lists.
I then looked for a fast way to emulate the idea with virtual index as
a secondary key and found this RB tree emulator:
https://www.cs.usfca.edu/~galles/visualization/RedBlack.html
and it showed me the picture I mentioned above:
02
/ \
01 14
/ \
03 15
\
16
I understand it is not 100% proof that index idea doesn't work
however it means that in order to apply the idea to this patch
some more changes are required additionally to what Peter
shared earlier.
>
> Regards,
> --
> Alex
>
>
>
