Share one arena across batch

ConflictSet.cpp

@@ -777,7 +777,8 @@ Vector<uint8_t> getSearchPath(Arena &arena, Node *n) {
 }
 
 bool checkRangeRead(Node *n, const std::span<const uint8_t> begin,
-                    const std::span<const uint8_t> end, int64_t readVersion) {
+                    const std::span<const uint8_t> end, int64_t readVersion,
+                    Arena &arena) {
   auto left = FirstGeqStepwise{n, begin};
   auto right = FirstGeqStepwise{n, end};
   bool leftDone = left.step();
@@ -829,7 +830,6 @@ bool checkRangeRead(Node *n, const std::span<const uint8_t> begin,
     return false;
   }
 
-  Arena arena{10 << 10};
   auto searchPath = getSearchPath(arena, left.n);
 
   for (auto *iter = nextPhysical(left.n, searchPath); iter != right.n;) {
@@ -945,6 +945,7 @@ void destroyTree(Node *root) {
 struct __attribute__((visibility("hidden"))) ConflictSet::Impl {
 
   void check(const ReadRange *reads, Result *result, int count) const {
+    Arena arena{64 << 10};
     for (int i = 0; i < count; ++i) {
       result[i] =
           reads[i].readVersion < oldestVersion ? TooOld
@@ -954,7 +955,7 @@ struct __attribute__((visibility("hidden"))) ConflictSet::Impl {
                                                            reads[i].begin.len),
                                   std::span<const uint8_t>(reads[i].end.p,
                                                            reads[i].end.len),
-                                  reads[i].readVersion)
+                                  reads[i].readVersion, arena)
                  : checkPointRead(root,
                                   std::span<const uint8_t>(reads[i].begin.p,
                                                            reads[i].begin.len),