Re: RFC: major runtime map changes

["Frank Ch. Eigler" <fche@redhat.com>]

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Hi -

hunt wrote:

> > different per-cpu maps will in general have different set of index
> > tuples?
> 
> The per-cpu maps are first aggregated into one map. 
> 
> Creating a pmap will actually create N+1 maps where N = number of cpus.
> The extra map will be the aggregation map.  When _stp_pmap_start(),
> stp_pmap_print(), or _stp_pmap_sort() are called, the per-cpu maps are
> summed into the aggregation map. [...]

OK.  Maybe it will be useful to avoid such copying, and do it
virtually, something like this:

- for pmap->lookup(key) iterate over map[cpu]->lookup(key) and aggregate
  on the fly

- for iteration, iterate over map[0], aggregating same keys over
  map[1..N], then follow that with an iteration over map[1] that skips
  those key tuples already handled for map[0], and so on.  The
  complexity of this may not be smaller than plain merge-then-iterate,
  but would eliminate data copying.

- for sorted iteration, sort each map[cpu], then do per-step
  "external merge"


- FChE

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