delta_for: Hoist end() out of the loop check

src/v/utils/delta_for.h

@@ -1006,12 +1006,13 @@ class deltafor_frame
     template<class PredT>
     const_iterator pred_search(value_t value) const {
         PredT pred;
-        for (auto it = begin(); it != end(); ++it) {
+        auto end_it = end();
+        for (auto it = begin(); it != end_it; ++it) {
             if (pred(*it, value)) {
                 return it;
             }
         }
-        return end();
+        return end_it;
     }
 
     std::array<value_t, buffer_depth> _head{};
@@ -1509,12 +1510,13 @@ class deltafor_column<value_t, details::delta_xor, max_frame_size>
     /// Find first value that matches the predicate
     const_iterator pred_search(
       value_t value, std::regular_invocable<value_t, value_t> auto pred) const {
-        for (auto it = this->begin(); it != this->end(); ++it) {
+        auto end_it = this->end();
+        for (auto it = this->begin(); it != end_it; ++it) {
             if (pred(*it, value)) {
                 return it;
             }
         }
-        return this->end();
+        return end_it;
     }
 };
 
@@ -1556,14 +1558,15 @@ class deltafor_column<value_t, details::delta_delta<value_t>, max_frame_size>
             }
             index += it->size();
         }
+        auto end_it = this->end();
         if (it != this->_frames.end()) {
             auto start = const_iterator(it, this->_frames.end(), 0, index);
-            for (; start != this->end(); ++start) {
+            for (; start != end_it; ++start) {
                 if (pred(*start, value)) {
                     return start;
                 }
             }
         }
-        return this->end();
+        return end_it;
     }
 };

src/v/utils/tests/delta_for_bench.cc

@@ -132,11 +132,16 @@ void append_tx_test(StoreT& store, int test_scale) {
 }
 
 template<class StoreT>
-void find_test(StoreT& store) {
+size_t find_test(StoreT& store) {
+    constexpr size_t batch = 10;
+    auto target = *store.last_value();
     perf_tests::start_measuring_time();
-    auto it = store.find(*store.last_value());
-    perf_tests::do_not_optimize(it);
+    for (size_t i = 0; i < batch; i++) {
+        auto it = store.find(target);
+        perf_tests::do_not_optimize(it);
+    }
     perf_tests::stop_measuring_time();
+    return batch;
 }
 
 template<class StoreT>
@@ -173,9 +178,11 @@ PERF_TEST(deltafor_bench, xor_column_append_tx2) {
     append_tx_test(column, 4097);
 }
 
-PERF_TEST(deltafor_bench, xor_frame_find_4K) { find_test(xor_frame_4K); }
+PERF_TEST(deltafor_bench, xor_frame_find_4K) { return find_test(xor_frame_4K); }
 
-PERF_TEST(deltafor_bench, xor_column_find_4K) { find_test(xor_column_4K); }
+PERF_TEST(deltafor_bench, xor_column_find_4K) {
+    return find_test(xor_column_4K);
+}
 
 PERF_TEST(deltafor_bench, xor_frame_at_4K) { at_test(xor_frame_4K); }
 
@@ -209,9 +216,13 @@ PERF_TEST(deltafor_bench, delta_column_append_tx2) {
     append_tx_test(column, 4097);
 }
 
-PERF_TEST(deltafor_bench, delta_frame_find_4K) { find_test(delta_frame_4K); }
+PERF_TEST(deltafor_bench, delta_frame_find_4K) {
+    return find_test(delta_frame_4K);
+}
 
-PERF_TEST(deltafor_bench, delta_column_find_4K) { find_test(delta_column_4K); }
+PERF_TEST(deltafor_bench, delta_column_find_4K) {
+    return find_test(delta_column_4K);
+}
 
 PERF_TEST(deltafor_bench, delta_column_find_4M) { at_test(delta_column_4M); }