});
#[derive(Eq, PartialEq)]
+#[repr(align(64))] // Force the size to 64 bytes
struct RouteGraphNode {
node_id: NodeId,
- lowest_fee_to_node: u64,
- total_cltv_delta: u32,
+ score: u64,
// The maximum value a yet-to-be-constructed payment path might flow through this node.
// This value is upper-bounded by us by:
// - how much is needed for a path being constructed
// - how much value can channels following this node (up to the destination) can contribute,
// considering their capacity and fees
value_contribution_msat: u64,
- /// The effective htlc_minimum_msat at this hop. If a later hop on the path had a higher HTLC
- /// minimum, we use it, plus the fees required at each earlier hop to meet it.
- path_htlc_minimum_msat: u64,
- /// All penalties incurred from this hop on the way to the destination, as calculated using
- /// channel scoring.
- path_penalty_msat: u64,
+ total_cltv_delta: u32,
/// The number of hops walked up to this node.
path_length_to_node: u8,
}
impl cmp::Ord for RouteGraphNode {
fn cmp(&self, other: &RouteGraphNode) -> cmp::Ordering {
- let other_score = cmp::max(other.lowest_fee_to_node, other.path_htlc_minimum_msat)
- .saturating_add(other.path_penalty_msat);
- let self_score = cmp::max(self.lowest_fee_to_node, self.path_htlc_minimum_msat)
- .saturating_add(self.path_penalty_msat);
- other_score.cmp(&self_score).then_with(|| other.node_id.cmp(&self.node_id))
+ other.score.cmp(&self.score).then_with(|| other.node_id.cmp(&self.node_id))
}
}
}
}
+// While RouteGraphNode can be laid out with fewer bytes, performance appears to be improved
+// substantially when it is laid out at exactly 64 bytes.
+//
+// Thus, we use `#[repr(C)]` on the struct to force a suboptimal layout and check that it stays 64
+// bytes here.
+#[cfg(any(ldk_bench, not(any(test, fuzzing))))]
+const _GRAPH_NODE_SMALL: usize = 64 - core::mem::size_of::<RouteGraphNode>();
+#[cfg(any(ldk_bench, not(any(test, fuzzing))))]
+const _GRAPH_NODE_FIXED_SIZE: usize = core::mem::size_of::<RouteGraphNode>() - 64;
+
/// A wrapper around the various hop representations.
///
/// Can be used to examine the properties of a hop,
}
}
+ /// Fetch the effective capacity of this hop.
+ ///
+ /// Note that this may be somewhat expensive, so calls to this should be limited and results
+ /// cached!
fn effective_capacity(&self) -> EffectiveCapacity {
match self {
CandidateRouteHop::FirstHop { details, .. } => EffectiveCapacity::ExactLiquidity {
/// Fee values should be updated only in the context of the whole path, see update_value_and_recompute_fees.
/// These fee values are useful to choose hops as we traverse the graph "payee-to-payer".
#[derive(Clone)]
+#[repr(C)] // Force fields to appear in the order we define them.
struct PathBuildingHop<'a> {
candidate: CandidateRouteHop<'a>,
- fee_msat: u64,
-
- /// All the fees paid *after* this channel on the way to the destination
- next_hops_fee_msat: u64,
- /// Fee paid for the use of the current channel (see candidate.fees()).
- /// The value will be actually deducted from the counterparty balance on the previous link.
- hop_use_fee_msat: u64,
+ /// If we've already processed a node as the best node, we shouldn't process it again. Normally
+ /// we'd just ignore it if we did as all channels would have a higher new fee, but because we
+ /// may decrease the amounts in use as we walk the graph, the actual calculated fee may
+ /// decrease as well. Thus, we have to explicitly track which nodes have been processed and
+ /// avoid processing them again.
+ was_processed: bool,
/// Used to compare channels when choosing the for routing.
/// Includes paying for the use of a hop and the following hops, as well as
/// an estimated cost of reaching this hop.
/// All penalties incurred from this channel on the way to the destination, as calculated using
/// channel scoring.
path_penalty_msat: u64,
- /// If we've already processed a node as the best node, we shouldn't process it again. Normally
- /// we'd just ignore it if we did as all channels would have a higher new fee, but because we
- /// may decrease the amounts in use as we walk the graph, the actual calculated fee may
- /// decrease as well. Thus, we have to explicitly track which nodes have been processed and
- /// avoid processing them again.
- was_processed: bool,
+
+ // The last 16 bytes are on the next cache line by default in glibc's malloc. Thus, we should
+ // only place fields which are not hot there. Luckily, the next three fields are only read if
+ // we end up on the selected path, and only in the final path layout phase, so we don't care
+ // too much if reading them is slow.
+
+ fee_msat: u64,
+
+ /// All the fees paid *after* this channel on the way to the destination
+ next_hops_fee_msat: u64,
+ /// Fee paid for the use of the current channel (see candidate.fees()).
+ /// The value will be actually deducted from the counterparty balance on the previous link.
+ hop_use_fee_msat: u64,
+
#[cfg(all(not(ldk_bench), any(test, fuzzing)))]
// In tests, we apply further sanity checks on cases where we skip nodes we already processed
// to ensure it is specifically in cases where the fee has gone down because of a decrease in
value_contribution_msat: u64,
}
+// Checks that the entries in the `find_route` `dist` map fit in (exactly) two standard x86-64
+// cache lines. Sadly, they're not guaranteed to actually lie on a cache line (and in fact,
+// generally won't, because at least glibc's malloc will align to a nice, big, round
+// boundary...plus 16), but at least it will reduce the amount of data we'll need to load.
+//
+// Note that these assertions only pass on somewhat recent rustc, and thus are gated on the
+// ldk_bench flag.
+#[cfg(ldk_bench)]
+const _NODE_MAP_SIZE_TWO_CACHE_LINES: usize = 128 - core::mem::size_of::<(NodeId, PathBuildingHop)>();
+#[cfg(ldk_bench)]
+const _NODE_MAP_SIZE_EXACTLY_CACHE_LINES: usize = core::mem::size_of::<(NodeId, PathBuildingHop)>() - 128;
+
impl<'a> core::fmt::Debug for PathBuildingHop<'a> {
fn fmt(&self, f: &mut core::fmt::Formatter) -> Result<(), core::fmt::Error> {
let mut debug_struct = f.debug_struct("PathBuildingHop");
score_params);
let path_penalty_msat = $next_hops_path_penalty_msat
.saturating_add(channel_penalty_msat);
- let new_graph_node = RouteGraphNode {
- node_id: src_node_id,
- lowest_fee_to_node: total_fee_msat,
- total_cltv_delta: hop_total_cltv_delta,
- value_contribution_msat,
- path_htlc_minimum_msat,
- path_penalty_msat,
- path_length_to_node,
- };
// Update the way of reaching $candidate.source()
// with the given short_channel_id (from $candidate.target()),
.saturating_add(path_penalty_msat);
if !old_entry.was_processed && new_cost < old_cost {
+ let new_graph_node = RouteGraphNode {
+ node_id: src_node_id,
+ score: cmp::max(total_fee_msat, path_htlc_minimum_msat).saturating_add(path_penalty_msat),
+ total_cltv_delta: hop_total_cltv_delta,
+ value_contribution_msat,
+ path_length_to_node,
+ };
targets.push(new_graph_node);
old_entry.next_hops_fee_msat = $next_hops_fee_msat;
old_entry.hop_use_fee_msat = hop_use_fee_msat;
// meaning how much will be paid in fees after this node (to the best of our knowledge).
// This data can later be helpful to optimize routing (pay lower fees).
macro_rules! add_entries_to_cheapest_to_target_node {
- ( $node: expr, $node_id: expr, $fee_to_target_msat: expr, $next_hops_value_contribution: expr,
- $next_hops_path_htlc_minimum_msat: expr, $next_hops_path_penalty_msat: expr,
+ ( $node: expr, $node_id: expr, $next_hops_value_contribution: expr,
$next_hops_cltv_delta: expr, $next_hops_path_length: expr ) => {
+ let fee_to_target_msat;
+ let next_hops_path_htlc_minimum_msat;
+ let next_hops_path_penalty_msat;
let skip_node = if let Some(elem) = dist.get_mut(&$node_id) {
let was_processed = elem.was_processed;
elem.was_processed = true;
+ fee_to_target_msat = elem.total_fee_msat;
+ next_hops_path_htlc_minimum_msat = elem.path_htlc_minimum_msat;
+ next_hops_path_penalty_msat = elem.path_penalty_msat;
was_processed
} else {
// Entries are added to dist in add_entry!() when there is a channel from a node.
// Because there are no channels from payee, it will not have a dist entry at this point.
// If we're processing any other node, it is always be the result of a channel from it.
debug_assert_eq!($node_id, maybe_dummy_payee_node_id);
+ fee_to_target_msat = 0;
+ next_hops_path_htlc_minimum_msat = 0;
+ next_hops_path_penalty_msat = 0;
false
};
let candidate = CandidateRouteHop::FirstHop {
details, payer_node_id: &our_node_id,
};
- add_entry!(&candidate, $fee_to_target_msat,
+ add_entry!(&candidate, fee_to_target_msat,
$next_hops_value_contribution,
- $next_hops_path_htlc_minimum_msat, $next_hops_path_penalty_msat,
+ next_hops_path_htlc_minimum_msat, next_hops_path_penalty_msat,
$next_hops_cltv_delta, $next_hops_path_length);
}
}
short_channel_id: *chan_id,
};
add_entry!(&candidate,
- $fee_to_target_msat,
+ fee_to_target_msat,
$next_hops_value_contribution,
- $next_hops_path_htlc_minimum_msat,
- $next_hops_path_penalty_msat,
+ next_hops_path_htlc_minimum_msat,
+ next_hops_path_penalty_msat,
$next_hops_cltv_delta, $next_hops_path_length);
}
}
// If not, targets.pop() will not even let us enter the loop in step 2.
None => {},
Some(node) => {
- add_entries_to_cheapest_to_target_node!(node, payee, 0, path_value_msat, 0, 0u64, 0, 0);
+ add_entries_to_cheapest_to_target_node!(node, payee, path_value_msat, 0, 0);
},
});
// Both these cases (and other cases except reaching recommended_value_msat) mean that
// paths_collection will be stopped because found_new_path==false.
// This is not necessarily a routing failure.
- 'path_construction: while let Some(RouteGraphNode { node_id, lowest_fee_to_node, total_cltv_delta, mut value_contribution_msat, path_htlc_minimum_msat, path_penalty_msat, path_length_to_node, .. }) = targets.pop() {
+ 'path_construction: while let Some(RouteGraphNode { node_id, total_cltv_delta, mut value_contribution_msat, path_length_to_node, .. }) = targets.pop() {
// Since we're going payee-to-payer, hitting our node as a target means we should stop
// traversing the graph and arrange the path out of what we found.
match network_nodes.get(&node_id) {
None => {},
Some(node) => {
- add_entries_to_cheapest_to_target_node!(node, node_id, lowest_fee_to_node,
- value_contribution_msat, path_htlc_minimum_msat, path_penalty_msat,
+ add_entries_to_cheapest_to_target_node!(node, node_id,
+ value_contribution_msat,
total_cltv_delta, path_length_to_node);
},
}
projects / rust-lightning / blobdiff