From: Matt Corallo Date: Fri, 5 Mar 2021 02:42:42 +0000 (-0500) Subject: Don't clone Features during Dijkstras graph walk X-Git-Tag: v0.0.14~37^2~2 X-Git-Url: http://git.bitcoin.ninja/?a=commitdiff_plain;h=4c754372628ed155f4babf9f443e05f13481b0f7;p=rust-lightning Don't clone Features during Dijkstras graph walk We currently copy the features objects in each channel as we walk the graph during route calculation. This implies a significant amount of malloc traffic as the features flags object are stored on the heap. Instead, because they features being referenced are in the network graph which we hold a reference to, we can simply store references to them. This nontrivially improves our get_route benchmark by around 5%. --- diff --git a/lightning/src/routing/router.rs b/lightning/src/routing/router.rs index 1e7d322c9..dc51b58ee 100644 --- a/lightning/src/routing/router.rs +++ b/lightning/src/routing/router.rs @@ -175,10 +175,15 @@ struct DummyDirectionalChannelInfo { /// 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)] -struct PathBuildingHop { - /// Hop-specific details unrelated to the path during the routing phase, - /// but rather relevant to the LN graph. - route_hop: RouteHop, +struct PathBuildingHop<'a> { + // The RouteHint fields which will eventually be used if this hop is used in a final Route. + // Note that node_features is calculated separately after our initial graph walk. + pubkey: PublicKey, + short_channel_id: u64, + channel_features: &'a ChannelFeatures, + fee_msat: u64, + cltv_expiry_delta: u32, + /// Minimal fees required to route to the source node of the current hop via any of its inbound channels. src_lowest_inbound_fees: RoutingFees, /// Fees of the channel used in this hop. @@ -217,15 +222,14 @@ struct PathBuildingHop { // Instantiated with a list of hops with correct data in them collected during path finding, // an instance of this struct should be further modified only via given methods. #[derive(Clone)] -struct PaymentPath { - hops: Vec, +struct PaymentPath<'a> { + hops: Vec<(PathBuildingHop<'a>, NodeFeatures)>, } -impl PaymentPath { - +impl<'a> PaymentPath<'a> { // TODO: Add a value_msat field to PaymentPath and use it instead of this function. fn get_value_msat(&self) -> u64 { - self.hops.last().unwrap().route_hop.fee_msat + self.hops.last().unwrap().0.fee_msat } fn get_total_fee_paid_msat(&self) -> u64 { @@ -234,9 +238,9 @@ impl PaymentPath { } let mut result = 0; // Can't use next_hops_fee_msat because it gets outdated. - for (i, hop) in self.hops.iter().enumerate() { + for (i, (hop, _)) in self.hops.iter().enumerate() { if i != self.hops.len() - 1 { - result += hop.route_hop.fee_msat; + result += hop.fee_msat; } } return result; @@ -254,7 +258,7 @@ impl PaymentPath { // This function, however, does not support arbitrarily increasing the value being transferred, // and the exception will be triggered. fn update_value_and_recompute_fees(&mut self, value_msat: u64) { - assert!(value_msat <= self.hops.last().unwrap().route_hop.fee_msat); + assert!(value_msat <= self.hops.last().unwrap().0.fee_msat); let mut total_fee_paid_msat = 0 as u64; for i in (0..self.hops.len()).rev() { @@ -265,10 +269,10 @@ impl PaymentPath { // htlc_minimum_msat of the current channel. Last hop is handled separately. let mut cur_hop_fees_msat = 0; if !last_hop { - cur_hop_fees_msat = self.hops.get(i + 1).unwrap().hop_use_fee_msat; + cur_hop_fees_msat = self.hops.get(i + 1).unwrap().0.hop_use_fee_msat; } - let mut cur_hop = self.hops.get_mut(i).unwrap(); + let mut cur_hop = &mut self.hops.get_mut(i).unwrap().0; cur_hop.next_hops_fee_msat = total_fee_paid_msat; // Overpay in fees if we can't save these funds due to htlc_minimum_msat. // We try to account for htlc_minimum_msat in scoring (add_entry!), so that nodes don't @@ -292,11 +296,11 @@ impl PaymentPath { if last_hop { // Final hop is a special case: it usually has just value_msat (by design), but also // it still could overpay for the htlc_minimum_msat. - cur_hop.route_hop.fee_msat = cur_hop_transferred_amount_msat; + cur_hop.fee_msat = cur_hop_transferred_amount_msat; } else { // Propagate updated fees for the use of the channels to one hop back, where they // will be actually paid (fee_msat). The last hop is handled above separately. - cur_hop.route_hop.fee_msat = cur_hop_fees_msat; + cur_hop.fee_msat = cur_hop_fees_msat; } // Fee for the use of the current hop which will be deducted on the previous hop. @@ -442,22 +446,6 @@ pub fn get_route(our_node_id: &PublicKey, network: &NetworkGraph, paye } }; - let mut targets = BinaryHeap::new(); //TODO: Do we care about switching to eg Fibbonaci heap? - let mut dist = HashMap::with_capacity(network.get_nodes().len()); - - // During routing, if we ignore a path due to an htlc_minimum_msat limit, we set this, - // indicating that we may wish to try again with a higher value, potentially paying to meet an - // htlc_minimum with extra fees while still finding a cheaper path. - let mut hit_minimum_limit; - - // When arranging a route, we select multiple paths so that we can make a multi-path payment. - // We start with a path_value of the exact amount we want, and if that generates a route we may - // return it immediately. Otherwise, we don't stop searching for paths until we have 3x the - // amount we want in total across paths, selecting the best subset at the end. - const ROUTE_CAPACITY_PROVISION_FACTOR: u64 = 3; - let recommended_value_msat = final_value_msat * ROUTE_CAPACITY_PROVISION_FACTOR as u64; - let mut path_value_msat = final_value_msat; - // Allow MPP only if we have a features set from somewhere that indicates the payee supports // it. If the payee supports it they're supposed to include it in the invoice, so that should // work reliably. @@ -473,25 +461,44 @@ pub fn get_route(our_node_id: &PublicKey, network: &NetworkGraph, paye // Prepare the data we'll use for payee-to-payer search by // inserting first hops suggested by the caller as targets. // Our search will then attempt to reach them while traversing from the payee node. - let mut first_hop_targets = HashMap::with_capacity(if first_hops.is_some() { first_hops.as_ref().unwrap().len() } else { 0 }); + let mut first_hop_targets: HashMap<_, (_, ChannelFeatures, _, NodeFeatures)> = + HashMap::with_capacity(if first_hops.is_some() { first_hops.as_ref().unwrap().len() } else { 0 }); if let Some(hops) = first_hops { for chan in hops { let short_channel_id = chan.short_channel_id.expect("first_hops should be filled in with usable channels, not pending ones"); if chan.remote_network_id == *our_node_id { return Err(LightningError{err: "First hop cannot have our_node_id as a destination.".to_owned(), action: ErrorAction::IgnoreError}); } - first_hop_targets.insert(chan.remote_network_id, (short_channel_id, chan.counterparty_features.clone(), chan.outbound_capacity_msat)); + first_hop_targets.insert(chan.remote_network_id, (short_channel_id, chan.counterparty_features.to_context(), chan.outbound_capacity_msat, chan.counterparty_features.to_context())); } if first_hop_targets.is_empty() { return Err(LightningError{err: "Cannot route when there are no outbound routes away from us".to_owned(), action: ErrorAction::IgnoreError}); } } + let empty_channel_features = ChannelFeatures::empty(); + + let mut targets = BinaryHeap::new(); //TODO: Do we care about switching to eg Fibbonaci heap? + let mut dist = HashMap::with_capacity(network.get_nodes().len()); + + // During routing, if we ignore a path due to an htlc_minimum_msat limit, we set this, + // indicating that we may wish to try again with a higher value, potentially paying to meet an + // htlc_minimum with extra fees while still finding a cheaper path. + let mut hit_minimum_limit; + + // When arranging a route, we select multiple paths so that we can make a multi-path payment. + // We start with a path_value of the exact amount we want, and if that generates a route we may + // return it immediately. Otherwise, we don't stop searching for paths until we have 3x the + // amount we want in total across paths, selecting the best subset at the end. + const ROUTE_CAPACITY_PROVISION_FACTOR: u64 = 3; + let recommended_value_msat = final_value_msat * ROUTE_CAPACITY_PROVISION_FACTOR as u64; + let mut path_value_msat = final_value_msat; + // We don't want multiple paths (as per MPP) share liquidity of the same channels. // This map allows paths to be aware of the channel use by other paths in the same call. // This would help to make a better path finding decisions and not "overbook" channels. // It is unaware of the directions (except for `outbound_capacity_msat` in `first_hops`). - let mut bookkeeped_channels_liquidity_available_msat = HashMap::new(); + let mut bookkeeped_channels_liquidity_available_msat = HashMap::with_capacity(network.get_nodes().len()); // Keeping track of how much value we already collected across other paths. Helps to decide: // - how much a new path should be transferring (upper bound); @@ -609,14 +616,11 @@ pub fn get_route(our_node_id: &PublicKey, network: &NetworkGraph, paye fee_proportional_millionths = fees.proportional_millionths; } PathBuildingHop { - route_hop: RouteHop { - pubkey: $dest_node_id.clone(), - node_features: NodeFeatures::empty(), - short_channel_id: 0, - channel_features: $chan_features.clone(), - fee_msat: 0, - cltv_expiry_delta: 0, - }, + pubkey: $dest_node_id.clone(), + short_channel_id: 0, + channel_features: $chan_features, + fee_msat: 0, + cltv_expiry_delta: 0, src_lowest_inbound_fees: RoutingFees { base_msat: fee_base_msat, proportional_millionths: fee_proportional_millionths, @@ -710,14 +714,11 @@ pub fn get_route(our_node_id: &PublicKey, network: &NetworkGraph, paye old_entry.next_hops_fee_msat = $next_hops_fee_msat; old_entry.hop_use_fee_msat = hop_use_fee_msat; old_entry.total_fee_msat = total_fee_msat; - old_entry.route_hop = RouteHop { - pubkey: $dest_node_id.clone(), - node_features: NodeFeatures::empty(), - short_channel_id: $chan_id.clone(), - channel_features: $chan_features.clone(), - fee_msat: 0, // This value will be later filled with hop_use_fee_msat of the following channel - cltv_expiry_delta: $directional_info.cltv_expiry_delta as u32, - }; + old_entry.pubkey = $dest_node_id.clone(); + old_entry.short_channel_id = $chan_id.clone(); + old_entry.channel_features = $chan_features; + old_entry.fee_msat = 0; // This value will be later filled with hop_use_fee_msat of the following channel + old_entry.cltv_expiry_delta = $directional_info.cltv_expiry_delta as u32; old_entry.channel_fees = $directional_info.fees; old_entry.htlc_minimum_msat = $directional_info.htlc_minimum_msat; old_entry.path_htlc_minimum_msat = path_htlc_minimum_msat; @@ -758,6 +759,7 @@ pub fn get_route(our_node_id: &PublicKey, network: &NetworkGraph, paye }; } + let empty_node_features = NodeFeatures::empty(); // Find ways (channels with destination) to reach a given node and store them // in the corresponding data structures (routing graph etc). // $fee_to_target_msat represents how much it costs to reach to this node from the payee, @@ -779,17 +781,16 @@ pub fn get_route(our_node_id: &PublicKey, network: &NetworkGraph, paye if !skip_node { if first_hops.is_some() { - if let Some(&(ref first_hop, ref features, ref outbound_capacity_msat)) = first_hop_targets.get(&$node_id) { - add_entry!(first_hop, *our_node_id, $node_id, dummy_directional_info, Some(outbound_capacity_msat / 1000), features.to_context(), $fee_to_target_msat, $next_hops_value_contribution, $next_hops_path_htlc_minimum_msat); + if let Some(&(ref first_hop, ref features, ref outbound_capacity_msat, _)) = first_hop_targets.get(&$node_id) { + add_entry!(first_hop, *our_node_id, $node_id, dummy_directional_info, Some(outbound_capacity_msat / 1000), features, $fee_to_target_msat, $next_hops_value_contribution, $next_hops_path_htlc_minimum_msat); } } - let features; - if let Some(node_info) = $node.announcement_info.as_ref() { - features = node_info.features.clone(); + let features = if let Some(node_info) = $node.announcement_info.as_ref() { + &node_info.features } else { - features = NodeFeatures::empty(); - } + &empty_node_features + }; if !features.requires_unknown_bits() { for chan_id in $node.channels.iter() { @@ -800,7 +801,7 @@ pub fn get_route(our_node_id: &PublicKey, network: &NetworkGraph, paye if first_hops.is_none() || chan.node_two != *our_node_id { if let Some(two_to_one) = chan.two_to_one.as_ref() { if two_to_one.enabled { - add_entry!(chan_id, chan.node_two, chan.node_one, two_to_one, chan.capacity_sats, chan.features, $fee_to_target_msat, $next_hops_value_contribution, $next_hops_path_htlc_minimum_msat); + add_entry!(chan_id, chan.node_two, chan.node_one, two_to_one, chan.capacity_sats, &chan.features, $fee_to_target_msat, $next_hops_value_contribution, $next_hops_path_htlc_minimum_msat); } } } @@ -808,7 +809,7 @@ pub fn get_route(our_node_id: &PublicKey, network: &NetworkGraph, paye if first_hops.is_none() || chan.node_one != *our_node_id { if let Some(one_to_two) = chan.one_to_two.as_ref() { if one_to_two.enabled { - add_entry!(chan_id, chan.node_one, chan.node_two, one_to_two, chan.capacity_sats, chan.features, $fee_to_target_msat, $next_hops_value_contribution, $next_hops_path_htlc_minimum_msat); + add_entry!(chan_id, chan.node_one, chan.node_two, one_to_two, chan.capacity_sats, &chan.features, $fee_to_target_msat, $next_hops_value_contribution, $next_hops_path_htlc_minimum_msat); } } } @@ -834,8 +835,8 @@ pub fn get_route(our_node_id: &PublicKey, network: &NetworkGraph, paye // If first hop is a private channel and the only way to reach the payee, this is the only // place where it could be added. if first_hops.is_some() { - if let Some(&(ref first_hop, ref features, ref outbound_capacity_msat)) = first_hop_targets.get(&payee) { - add_entry!(first_hop, *our_node_id, payee, dummy_directional_info, Some(outbound_capacity_msat / 1000), features.to_context(), 0, path_value_msat, 0); + if let Some(&(ref first_hop, ref features, ref outbound_capacity_msat, _)) = first_hop_targets.get(&payee) { + add_entry!(first_hop, *our_node_id, payee, dummy_directional_info, Some(outbound_capacity_msat / 1000), features, 0, path_value_msat, 0); } } @@ -858,7 +859,7 @@ pub fn get_route(our_node_id: &PublicKey, network: &NetworkGraph, paye // it matters only if the fees are exactly the same. for hop in last_hops.iter() { let have_hop_src_in_graph = - if let Some(&(ref first_hop, ref features, ref outbound_capacity_msat)) = first_hop_targets.get(&hop.src_node_id) { + if let Some(&(ref first_hop, ref features, ref outbound_capacity_msat, _)) = first_hop_targets.get(&hop.src_node_id) { // If this hop connects to a node with which we have a direct channel, ignore // the network graph and add both the hop and our direct channel to // the candidate set. @@ -867,7 +868,7 @@ pub fn get_route(our_node_id: &PublicKey, network: &NetworkGraph, paye // bit lazy here. In the future, we should pull them out via our // ChannelManager, but there's no reason to waste the space until we // need them. - add_entry!(first_hop, *our_node_id , hop.src_node_id, dummy_directional_info, Some(outbound_capacity_msat / 1000), features.to_context(), 0, path_value_msat, 0); + add_entry!(first_hop, *our_node_id , hop.src_node_id, dummy_directional_info, Some(outbound_capacity_msat / 1000), features, 0, path_value_msat, 0); true } else { // In any other case, only add the hop if the source is in the regular network @@ -887,7 +888,7 @@ pub fn get_route(our_node_id: &PublicKey, network: &NetworkGraph, paye htlc_maximum_msat: hop.htlc_maximum_msat, fees: hop.fees, }; - add_entry!(hop.short_channel_id, hop.src_node_id, payee, directional_info, None::, ChannelFeatures::empty(), 0, path_value_msat, 0); + add_entry!(hop.short_channel_id, hop.src_node_id, payee, directional_info, None::, &empty_channel_features, 0, path_value_msat, 0); } } @@ -910,34 +911,34 @@ pub fn get_route(our_node_id: &PublicKey, network: &NetworkGraph, paye // traversing the graph and arrange the path out of what we found. if pubkey == *our_node_id { let mut new_entry = dist.remove(&our_node_id).unwrap(); - let mut ordered_hops = vec!(new_entry.clone()); + let mut ordered_hops = vec!((new_entry.clone(), NodeFeatures::empty())); 'path_walk: loop { - if let Some(&(_, ref features, _)) = first_hop_targets.get(&ordered_hops.last().unwrap().route_hop.pubkey) { - ordered_hops.last_mut().unwrap().route_hop.node_features = features.to_context(); - } else if let Some(node) = network.get_nodes().get(&ordered_hops.last().unwrap().route_hop.pubkey) { + if let Some(&(_, _, _, ref features)) = first_hop_targets.get(&ordered_hops.last().unwrap().0.pubkey) { + ordered_hops.last_mut().unwrap().1 = features.clone(); + } else if let Some(node) = network.get_nodes().get(&ordered_hops.last().unwrap().0.pubkey) { if let Some(node_info) = node.announcement_info.as_ref() { - ordered_hops.last_mut().unwrap().route_hop.node_features = node_info.features.clone(); + ordered_hops.last_mut().unwrap().1 = node_info.features.clone(); } else { - ordered_hops.last_mut().unwrap().route_hop.node_features = NodeFeatures::empty(); + ordered_hops.last_mut().unwrap().1 = NodeFeatures::empty(); } } else { // We should be able to fill in features for everything except the last // hop, if the last hop was provided via a BOLT 11 invoice (though we // should be able to extend it further as BOLT 11 does have feature // flags for the last hop node itself). - assert!(ordered_hops.last().unwrap().route_hop.pubkey == *payee); + assert!(ordered_hops.last().unwrap().0.pubkey == *payee); } // Means we succesfully traversed from the payer to the payee, now // save this path for the payment route. Also, update the liquidity // remaining on the used hops, so that we take them into account // while looking for more paths. - if ordered_hops.last().unwrap().route_hop.pubkey == *payee { + if ordered_hops.last().unwrap().0.pubkey == *payee { break 'path_walk; } - new_entry = match dist.remove(&ordered_hops.last().unwrap().route_hop.pubkey) { + new_entry = match dist.remove(&ordered_hops.last().unwrap().0.pubkey) { Some(payment_hop) => payment_hop, // We can't arrive at None because, if we ever add an entry to targets, // we also fill in the entry in dist (see add_entry!). @@ -946,13 +947,13 @@ pub fn get_route(our_node_id: &PublicKey, network: &NetworkGraph, paye // We "propagate" the fees one hop backward (topologically) here, // so that fees paid for a HTLC forwarding on the current channel are // associated with the previous channel (where they will be subtracted). - ordered_hops.last_mut().unwrap().route_hop.fee_msat = new_entry.hop_use_fee_msat; - ordered_hops.last_mut().unwrap().route_hop.cltv_expiry_delta = new_entry.route_hop.cltv_expiry_delta; - ordered_hops.push(new_entry.clone()); + ordered_hops.last_mut().unwrap().0.fee_msat = new_entry.hop_use_fee_msat; + ordered_hops.last_mut().unwrap().0.cltv_expiry_delta = new_entry.cltv_expiry_delta; + ordered_hops.push((new_entry.clone(), NodeFeatures::empty())); } - ordered_hops.last_mut().unwrap().route_hop.fee_msat = value_contribution_msat; - ordered_hops.last_mut().unwrap().hop_use_fee_msat = 0; - ordered_hops.last_mut().unwrap().route_hop.cltv_expiry_delta = final_cltv; + ordered_hops.last_mut().unwrap().0.fee_msat = value_contribution_msat; + ordered_hops.last_mut().unwrap().0.hop_use_fee_msat = 0; + ordered_hops.last_mut().unwrap().0.cltv_expiry_delta = final_cltv; let mut payment_path = PaymentPath {hops: ordered_hops}; @@ -973,8 +974,8 @@ pub fn get_route(our_node_id: &PublicKey, network: &NetworkGraph, paye // Remember that we used these channels so that we don't rely // on the same liquidity in future paths. let mut prevented_redundant_path_selection = false; - for payment_hop in payment_path.hops.iter() { - let channel_liquidity_available_msat = bookkeeped_channels_liquidity_available_msat.get_mut(&payment_hop.route_hop.short_channel_id).unwrap(); + for (payment_hop, _) in payment_path.hops.iter() { + let channel_liquidity_available_msat = bookkeeped_channels_liquidity_available_msat.get_mut(&payment_hop.short_channel_id).unwrap(); let mut spent_on_hop_msat = value_contribution_msat; let next_hops_fee_msat = payment_hop.next_hops_fee_msat; spent_on_hop_msat += next_hops_fee_msat; @@ -995,7 +996,7 @@ pub fn get_route(our_node_id: &PublicKey, network: &NetworkGraph, paye // we'll probably end up picking the same path again on the next iteration. // Decrease the available liquidity of a hop in the middle of the path. let victim_liquidity = bookkeeped_channels_liquidity_available_msat.get_mut( - &payment_path.hops[(payment_path.hops.len() - 1) / 2].route_hop.short_channel_id).unwrap(); + &payment_path.hops[(payment_path.hops.len() - 1) / 2].0.short_channel_id).unwrap(); *victim_liquidity = 0; } @@ -1120,7 +1121,7 @@ pub fn get_route(our_node_id: &PublicKey, network: &NetworkGraph, paye // Now, substract the overpaid value from the most-expensive path. // TODO: this could also be optimized by also sorting by feerate_per_sat_routed, // so that the sender pays less fees overall. And also htlc_minimum_msat. - cur_route.sort_by_key(|path| { path.hops.iter().map(|hop| hop.channel_fees.proportional_millionths as u64).sum::() }); + cur_route.sort_by_key(|path| { path.hops.iter().map(|hop| hop.0.channel_fees.proportional_millionths as u64).sum::() }); let expensive_payment_path = cur_route.first_mut().unwrap(); // We already dropped all the small channels above, meaning all the // remaining channels are larger than remaining overpaid_value_msat. @@ -1138,7 +1139,16 @@ pub fn get_route(our_node_id: &PublicKey, network: &NetworkGraph, paye drawn_routes.sort_by_key(|paths| paths.iter().map(|path| path.get_total_fee_paid_msat()).sum::()); let mut selected_paths = Vec::>::new(); for payment_path in drawn_routes.first().unwrap() { - selected_paths.push(payment_path.hops.iter().map(|payment_hop| payment_hop.route_hop.clone()).collect()); + selected_paths.push(payment_path.hops.iter().map(|(payment_hop, node_features)| { + RouteHop { + pubkey: payment_hop.pubkey, + node_features: node_features.clone(), + short_channel_id: payment_hop.short_channel_id, + channel_features: payment_hop.channel_features.clone(), + fee_msat: payment_hop.fee_msat, + cltv_expiry_delta: payment_hop.cltv_expiry_delta, + } + }).collect()); } if let Some(features) = &payee_features {