vincenzopalazzo
/
arti
1
0
Fork 0
Code Issues Pull Requests Packages Projects Releases Wiki Activity

NetDir: Use less space in hash tables 

We previously kept missing-MD entries and present-MD entries all in
the same HashSet, which resulted in using more slack space than we
need.  Now we use separate tables, so we can drop missing-MD
entries as we move forward.

Also, when constructing a NetDir, set its hash tables to their final
capacities.

This also lets us simplify some of our missing-md-listing code a
lot.
This commit is contained in:
Nick Mathewson 2022-03-16 11:12:15 -04:00
parent 9593cf637a
commit 233613cd79
1 changed files with 32 additions and 58 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

90
crates/tor-netdir/src/lib.rs
View File

@ -150,28 +150,14 @@ impl SubnetConfig {
}
}
/// Internal type: either a microdescriptor, or the digest for a
/// microdescriptor that we want.
/// Internal type to hold an Arc<Microdesc>.
///
/// This is a separate type so we can use a HashSet instead of
/// HashMap.
#[derive(Clone, Debug)]
enum MdEntry {
/// A microdescriptor that is wanted but not present.
Absent {
/// Index of the routerstatus entry that wants this microdesc.
rs_idx: usize,
/// Content digest of the microdescriptor.
// TODO: I wanted to make this a reference at first, but that's
// nontrival. At this point I'm not 100% sure it would be a good
// idea.
d: MdDigest,
},
/// A microdescriptor that we have.
Present {
/// The microdescriptor itself.
md: Arc<Microdesc>,
},
struct MdEntry {
/// The microdescriptor itself.
md: Arc<Microdesc>,
}
impl std::borrow::Borrow<MdDigest> for MdEntry {
@ -183,10 +169,7 @@ impl std::borrow::Borrow<MdDigest> for MdEntry {
impl MdEntry {
/// Return the digest for this entry.
fn digest(&self) -> &MdDigest {
match self {
MdEntry::Absent { d, .. } => d,
MdEntry::Present { md, .. } => md.digest(),
}
self.md.digest()
}
}
@ -277,6 +260,9 @@ pub struct NetDir {
/// Map from SHA256 digest of microdescriptors to the
/// microdescriptors themselves.
mds: HashSet<MdEntry>,
/// Map from SHA256 of _missing_ microdescriptors to the position of their
/// corresponding routerstatus indices within `consensus`.
rs_idx_by_missing: HashMap<MdDigest, usize>,
/// Map from ed25519 identity to index of the routerstatus within
/// `self.consensus.relays()`.
///
@ -373,14 +359,13 @@ impl PartialNetDir {
// Compute the weights we'll want to use for these relays.
let weights = weight::WeightSet::from_consensus(&consensus, &params);
let mds = consensus
let n_relays = consensus.relays().len();
let rs_idx_by_missing = consensus
.relays()
.iter()
.enumerate()
.map(|(rs_idx, rs)| MdEntry::Absent {
rs_idx,
d: *rs.md_digest(),
})
.map(|(rs_idx, rs)| (*rs.md_digest(), rs_idx))
.collect();
let rs_idx_by_rsa = consensus
@ -393,9 +378,10 @@ impl PartialNetDir {
let netdir = NetDir {
consensus: Arc::new(consensus),
params,
mds,
mds: HashSet::with_capacity(n_relays),
rs_idx_by_missing,
rs_idx_by_rsa: Arc::new(rs_idx_by_rsa),
rs_idx_by_ed: HashMap::new(),
rs_idx_by_ed: HashMap::with_capacity(n_relays),
weights,
};
@ -412,11 +398,8 @@ impl PartialNetDir {
pub fn fill_from_previous_netdir<'a>(&mut self, prev: &'a NetDir) -> Vec<&'a MdDigest> {
let mut loaded = Vec::new();
for ent in &prev.mds {
if let MdEntry::Present { md, .. } = ent {
if self.netdir.mds.contains(md.digest()) {
loaded.push(md.digest());
self.netdir.add_arc_microdesc(Arc::clone(md));
}
if self.netdir.add_arc_microdesc(ent.md.clone()) {
loaded.push(ent.md.digest());
}
}
loaded
@ -466,23 +449,23 @@ impl NetDir {
/// Return true if we wanted it, and false otherwise.
#[allow(clippy::missing_panics_doc)] // Can't panic on valid object.
fn add_arc_microdesc(&mut self, md: Arc<Microdesc>) -> bool {
if let Some(prev_ent) = self.mds.take(md.digest()) {
if let MdEntry::Absent { rs_idx, .. } = prev_ent {
assert_eq!(self.consensus.relays()[rs_idx].md_digest(), md.digest());
if let Some(rs_idx) = self.rs_idx_by_missing.remove(md.digest()) {
assert_eq!(self.consensus.relays()[rs_idx].md_digest(), md.digest());
// There should never be two approved MDs in the same
// consensus listing the same ID... but if there is,
// we'll let the most recent one win.
self.rs_idx_by_ed.insert(*md.ed25519_id(), rs_idx);
// There should never be two approved MDs in the same
// consensus listing the same ID... but if there is,
// we'll let the most recent one win.
self.rs_idx_by_ed.insert(*md.ed25519_id(), rs_idx);
// Happy path: we did indeed want this one.
self.mds.insert(MdEntry::Present { md });
// Happy path: we did indeed want this one.
self.mds.insert(MdEntry { md });
return true;
} else {
// We already had this.
self.mds.insert(prev_ent);
// Save some space in the missing-descriptor list.
if self.rs_idx_by_missing.len() < self.rs_idx_by_missing.capacity() / 4 {
self.rs_idx_by_missing.shrink_to_fit();
}
return true;
}
// Either we already had it, or we never wanted it at all.
@ -495,10 +478,7 @@ impl NetDir {
&'a self,
rs: &'a netstatus::MdConsensusRouterStatus,
) -> UncheckedRelay<'a> {
let md = match self.mds.get(rs.md_digest()) {
Some(MdEntry::Present { md }) => Some(Arc::as_ref(md)),
_ => None,
};
let md = self.mds.get(rs.md_digest()).map(|ent| ent.md.as_ref());
UncheckedRelay { rs, md }
}
@ -864,13 +844,7 @@ impl NetDir {
impl MdReceiver for NetDir {
fn missing_microdescs(&self) -> Box<dyn Iterator<Item = &MdDigest> + '_> {
Box::new(self.consensus.relays().iter().filter_map(move |rs| {
let d = rs.md_digest();
match self.mds.get(d) {
Some(MdEntry::Absent { d, .. }) => Some(d),
_ => None,
}
}))
Box::new(self.rs_idx_by_missing.keys())
}
fn add_microdesc(&mut self, md: Microdesc) -> bool {
self.add_arc_microdesc(Arc::new(md))