# UNDF: UNDF-2026-000000026
diff --git a/src/osd/OSDMap.cc b/src/osd/OSDMap.cc
--- a/src/osd/OSDMap.cc
+++ b/src/osd/OSDMap.cc
@@ -5818,6 +5818,8 @@ int OSDMap::calc_pg_upmaps(
   while (max--) {
     ldout(cct, 30) << "Top of loop #" << max+1 << dendl;
     // build overfull and underfull
     set<int> overfull;
     set<int> more_overfull;
     bool using_more_overfull = false;
     vector<int> underfull;
     vector<int> more_underfull;
     fill_overfull_underfull(cct, deviation_osd, max_deviation,
                             overfull, more_overfull,
                             underfull, more_underfull);
+    // Pre-build O(1) lookup sets — underfull/more_underfull are read-only in
+    // the scan loops below, so unordered_set avoids O(N×U) std::find calls.
+    std::unordered_set<int> underfull_set(underfull.begin(), underfull.end());
+    std::unordered_set<int> more_underfull_set(more_underfull.begin(), more_underfull.end());

@@ -5979,8 +5981,7 @@ int OSDMap::calc_pg_upmaps(
     for (auto& [deviation, osd] : deviation_osd) {
-      if (std::find(underfull.begin(), underfull.end(), osd) ==
-                    underfull.end())
+      if (underfull_set.find(osd) == underfull_set.end())
         break;
       float target = osd_weight[osd] * pgs_per_weight;

diff --git a/src/crush/CrushWrapper.cc b/src/crush/CrushWrapper.cc
--- a/src/crush/CrushWrapper.cc
+++ b/src/crush/CrushWrapper.cc
@@ -4118,6 +4118,8 @@ int CrushWrapper::try_remap_rule(
     for (int pos = 0; pos < fanout; ++pos) {
       if (type > 0) {
         // non-leaf: no change
       } else {
         // leaf
         bool replaced = false;
         if (overfull.count(*i)) {
+          // Build orig_set once per leaf slot — O(1) membership below
+          std::unordered_set<int> orig_set(orig.begin(), orig.end());
           for (auto item : underfull) {
             if (used.count(item)) continue;
             if (!subtree_contains(from, item)) continue;
-            if (std::find(orig.begin(), orig.end(), item) != orig.end()) {
+            if (orig_set.count(item)) {
               ldout(cct, 20) << __func__ << "   in orig " << orig << dendl;
               continue;
             }
@@ -4152,8 +4154,6 @@ int CrushWrapper::try_remap_rule(
           if (!replaced) {
             for (auto item : more_underfull) {
               if (used.count(item)) continue;
               if (!subtree_contains(from, item)) continue;
-              if (std::find(orig.begin(), orig.end(), item) != orig.end()) {
+              if (orig_set.count(item)) {
                 ldout(cct, 20) << __func__ << "   in orig " << orig << dendl;
                 continue;
               }