For nodes with many channels this is a tremendous improvement in pay
performance. PR #7611 improves payment performance from 15 seconds to
13.5 seconds on one of our nodes. This commit improves payment
performance from 13.5 seconds to 5.7 seconds.
Changelog-Fixed: Improved pathfinding speed for large nodes.
This minimizes the need to convert back and forth from and to sat
values, and it also removes a new instance of sats in the public
interface (`channel_hints`).
Suggested-By: Rusty Russell <@rustyrussell>
We were ignoring more reliable information because of the
stricter-is-better logic. This meant that we were also ignoring local
channel information, despite knowing better.
By simplifying the logic to pick the one with the newer timestamp we
ensure that later observations always trump earlier ones. There is a
bit of interplay between the relaxation of the constraints updating
the timestamp, and comparing to real observation timestamps, but that
should not impact us for local channels.
If we have a large channel, fail to send through a small amount, and
then add a `channel_hint`, then it can happen that the call to
`channel_hint_set_update` is already late enough that it refills the
1msat we removed from the attempted amount, thus making the edge we
just excluded eligible again, which can lead into an infinite loop.
We slow down the updating of the channel_hints to once every
hysteresis timeout. This allows us to set tight constraints, while not
incurring in the accidental relaxation issue.
