max_entries of flow_directions map sets from configuration

[bareckidarek]

The flow_directions map with hardcoded max_entries as 1 << 24 needs to lock over 2GB of memory.

sudo bpftool map show name flow_directions
563: lru_hash  name flow_directions  flags 0x0
	key 43B  value 1B  max_entries 16777216  memlock 2013267008B
	btf_id 664

This PR sets max entries from user configuration as for aggregate_flows. With a default value (5000) needs about 650KB.

sudo bpftool map show name flow_directions
556: lru_hash  name flow_directions  flags 0x0
	key 43B  value 1B  max_entries 5000  memlock 652160B
	btf_id 656

The key flow_id is pretty heavy (43B), and having it readable in the flow_directions map is unnecessary. I analysed if there is a better key to use, but found nothing yet.

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 79.43%. Comparing base (d7d75a1) to head (9f28c6b).

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #959      +/-   ##
==========================================
+ Coverage   71.45%   79.43%   +7.98%     
==========================================
  Files         130      131       +1     
  Lines       10319    10330      +11     
==========================================
+ Hits         7373     8206     +833     
+ Misses       2314     1603     -711     
+ Partials      632      521     -111     

Flag	Coverage Δ
integration-test	54.31% <100.00%> (+0.02%)	⬆️
k8s-integration-test	58.05% <100.00%> (-0.25%)	⬇️
oats-test	35.94% <0.00%> (-0.01%)	⬇️
unittests	47.58% <0.00%> (?)

Flags with carried forward coverage won't be shown. Click here to find out more.

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.

[grcevski]

LGTM! Nice catch!

[grcevski]

Thanks again @bareckidarek !