Make `find_route`'s `dist` map elements fit in 128 bytes

[rust-lightning] / lightning / src / routing / router.rs

diff --git a/lightning/src/routing/router.rs b/lightning/src/routing/router.rs
index 7b1df46fb65854e448c70e21e4c23eda20e7a404..652c8cd32f2cec946db87fddaf3db99ceffe5632 100644 (file)
--- a/lightning/src/routing/router.rs
+++ b/lightning/src/routing/router.rs
@@ -1186,6 +1186,10 @@ impl<'a> CandidateRouteHop<'a> {
                }
        }
 
+       /// 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 {
@@ -1341,6 +1345,18 @@ struct PathBuildingHop<'a> {
        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");