diff --git a/crates/rib/src/table/mod.rs b/crates/rib/src/table/mod.rs
index 0b3d5aa..4fc5ad6 100644
--- a/crates/rib/src/table/mod.rs
+++ b/crates/rib/src/table/mod.rs
@@ -193,13 +193,16 @@ impl Row {
             .position(|(index, path)| path.peer() == peer && self.path_id(index) == path_id)
     }
 
-    fn push(&mut self, path: Path, path_id: u32) {
+    /// Adds a route. `peers` is how many peers the table has: a prefix
+    /// that one of them announces, the others mostly announce too, so a
+    /// row is given room for that many at its first growth.
+    fn push(&mut self, path: Path, path_id: u32, peers: usize) {
         if path_id != 0 && self.path_ids.is_empty() {
             self.path_ids = vec![0; self.paths.len()];
         }
-        push_tight(&mut self.paths, path);
+        push_tight(&mut self.paths, path, peers);
         if !self.path_ids.is_empty() {
-            push_tight(&mut self.path_ids, path_id);
+            push_tight(&mut self.path_ids, path_id, peers);
         }
     }
 
@@ -855,12 +858,25 @@ fn spread(hash: u64, count: usize) -> usize {
     ((stirred * count as u64) >> 32) as usize
 }
 
+/// The most room a row is given at its first growth, however many peers
+/// there are: a route server's clients do not all announce every prefix.
+const FIRST_ROOM: usize = 8;
+
 /// Adds to a vector without the doubling that `push` does: a row of a few
-/// hundred routes should not hold room for as many again. Grows by a
-/// quarter, which keeps adding cheap on average.
-fn push_tight<T>(vec: &mut Vec<T>, value: T) {
+/// hundred routes should not hold room for as many again. The first
+/// growth is to `expected` (at most [`FIRST_ROOM`]), since with several
+/// full tables nearly every row gets that many routes, and growing a row
+/// one route at a time was a twelfth of what taking in four tables cost.
+/// After that it grows by a quarter, which keeps adding cheap on average.
+fn push_tight<T>(vec: &mut Vec<T>, value: T, expected: usize) {
     if vec.len() == vec.capacity() {
-        vec.reserve_exact((vec.len() / 4).max(1));
+        let first = expected.min(FIRST_ROOM);
+        let more = if vec.capacity() < first {
+            first - vec.len()
+        } else {
+            (vec.len() / 4).max(1)
+        };
+        vec.reserve_exact(more);
     }
     vec.push(value);
 }
@@ -902,7 +918,7 @@ impl Shard {
 
         let (outcome, best_changed) = match row.position(peer, path_id) {
             None => {
-                row.push(path, path_id);
+                row.push(path, path_id, self.peers.len());
                 self.routes += 1;
                 let outcome = Outcome {
                     added: 1,
diff --git a/crates/rib/src/table/tests.rs b/crates/rib/src/table/tests.rs
index 54500db..fa8dbe2 100644
--- a/crates/rib/src/table/tests.rs
+++ b/crates/rib/src/table/tests.rs
@@ -957,13 +957,13 @@ fn a_row_can_hold_more_routes_than_a_sixteen_bit_index_counts() {
     let mut scratch = select::Scratch::default();
     let count = usize::from(u16::MAX) + 10;
     for path_id in 2..=count as u32 {
-        row.push(path(&worse), path_id);
+        row.push(path(&worse), path_id, peers.len());
     }
     // Equal routes from one peer: the lowest identifier is the best.
     assert!(!select::after_add(&mut row, &peers, &mut scratch));
     assert_eq!(row.best(), 0);
 
-    row.push(path(&better), count as u32 + 1);
+    row.push(path(&better), count as u32 + 1, peers.len());
     assert!(select::after_add(&mut row, &peers, &mut scratch));
     assert_eq!(row.best(), count);
     assert_eq!(row.route(row.best()).path_id, count as u32 + 1);
diff --git a/docs/content/docs/development/testing.md b/docs/content/docs/development/testing.md
index 67f2967..f13f761 100644
--- a/docs/content/docs/development/testing.md
+++ b/docs/content/docs/development/testing.md
@@ -214,6 +214,7 @@ environment variables that control the run.
 | `HOLD_SECS` | How long the sessions stay open after the table is sent | 30 |
 | `FREQ` | The sampling frequency in hertz | 1999 |
 | `OUT` | The directory for the results | `~/profile` |
+| `JEMALLOC_CONF` | jemalloc options for the daemon (its `MALLOC_CONF`), for example `thp:always` | none |
 
 When run through `scripts/linux-vm.sh`, pass the variables with `env`,
 because the virtual machine does not receive the host's environment:
diff --git a/scripts/profile/full-table.sh b/scripts/profile/full-table.sh
index b776584..1318454 100755
--- a/scripts/profile/full-table.sh
+++ b/scripts/profile/full-table.sh
@@ -104,7 +104,9 @@ if [ "$kernel" = 1 ]; then
     echo 'kernel { stale_seconds: 0 }' >> "$out/daemon.textpb"
 fi
 
-run "$daemon_bin" "$out/daemon.textpb" --level warn > "$out/daemon.log" 2>&1 &
+# `JEMALLOC_CONF`, if set, is jemalloc's MALLOC_CONF for the daemon:
+# "thp:always", say. The symbols are prefixed, hence the variable's name.
+run env _RJEM_MALLOC_CONF="${JEMALLOC_CONF:-}" "$daemon_bin" "$out/daemon.textpb" --level warn > "$out/daemon.log" 2>&1 &
 for _ in $(seq 100); do
     run curl -sf http://127.0.0.1:8080/api/status > /dev/null 2>&1 && break
     sleep 0.1