build: fix the heap profiling build and cover it in CI

.github/workflows/install-build-env.sh

@@ -109,6 +109,7 @@ group "configure.py"
     --compiler "$CPP"           \
     --c-compiler "$CC"          \
     --mode "$MODE"              \
+    --heap-profiling            \
     "${cook_args[@]}"           \
     "${ccache_opt[@]}"          \
     $OPTIONS                    \

include/seastar/core/chunked_hash_map.hh

@@ -22,7 +22,23 @@
 
 #include <seastar/core/chunked_vector.hh>
 
+// abseil LTS 20220623 and earlier include <ciso646> from
+// absl/base/options.h. libstdc++ 16 warns on that header for C++20 and later,
+// and seastar builds with -Werror.
+#if defined(__clang__)
+#pragma clang diagnostic push
+#pragma clang diagnostic ignored "-W#warnings"
+#elif defined(__GNUC__)
+#pragma GCC diagnostic push
+#pragma GCC diagnostic ignored "-Wcpp"
+#endif
 #include <absl/hash/hash.h>
+#if defined(__clang__)
+#pragma clang diagnostic pop
+#elif defined(__GNUC__)
+#pragma GCC diagnostic pop
+#endif
+
 #include <ankerl/unordered_dense.h>
 #include <fmt/format.h>
 #include <fmt/ranges.h>

tests/unit/alloc_test.cc

@@ -591,7 +591,15 @@ SEASTAR_TEST_CASE(test_sampled_profile_collection_small)
         BOOST_REQUIRE_EQUAL(stats.size(), 0);
     }
 
-    std::size_t count = 100;
+    // The two loops below are distinct call sites and the assertions require
+    // both of them to be sampled, so each loop has to cover enough sampling
+    // intervals that missing one entirely is not plausible. The sampler draws
+    // the gap to the next sample from an exponential distribution whose mean is
+    // the sampling interval, so a loop allocating N intervals worth of bytes
+    // records nothing with probability e^-N. count/2 * 10 bytes against the 100
+    // byte interval below is N=50, putting the chance of recording one call
+    // site instead of two at about 2*e^-50.
+    std::size_t count = 1000;
     std::vector<volatile char*> ptrs(count);
 
     seastar::memory::set_heap_profiling_sampling_rate(100);
@@ -615,20 +623,20 @@ SEASTAR_TEST_CASE(test_sampled_profile_collection_small)
         auto stats1 = seastar::memory::sampled_memory_profile();
 
         // two back-to-back copies of the sample should have the same value
-        BOOST_CHECK_EQUAL(stats0, stats1);
+        BOOST_CHECK_EQUAL_COLLECTIONS(stats0.begin(), stats0.end(), stats1.begin(), stats1.end());
 
         // check that we get the same value from the raw array iterface
         std::vector<seastar::memory::allocation_site> stats2(stats0.size());
         auto sz2 = seastar::memory::sampled_memory_profile(stats2.data(), stats2.size());
         BOOST_CHECK_EQUAL(stats0.size(), sz2);
-        BOOST_CHECK_EQUAL(stats0, stats2);
+        BOOST_CHECK_EQUAL_COLLECTIONS(stats0.begin(), stats0.end(), stats2.begin(), stats2.end());
 
         // check with +1 size, we expect to still only get size elements
         std::vector<seastar::memory::allocation_site> stats3(stats0.size() + 1);
         auto sz3 = seastar::memory::sampled_memory_profile(stats3.data(), stats3.size());
         BOOST_CHECK_EQUAL(stats0.size(), sz3);
         stats3.resize(sz3);
-        BOOST_CHECK_EQUAL(stats0, stats3);
+        BOOST_CHECK_EQUAL_COLLECTIONS(stats0.begin(), stats0.end(), stats3.begin(), stats3.end());
 
         return stats0;
     };
@@ -668,7 +676,16 @@ SEASTAR_TEST_CASE(test_sampled_profile_collection_large)
     std::size_t count = 100;
     std::vector<volatile char*> ptrs(count);
 
-    seastar::memory::set_heap_profiling_sampling_rate(1000000);
+    // Both loops have to be sampled, as in
+    // test_sampled_profile_collection_small: count/2 * 100000 bytes against
+    // this interval is N=25 intervals per loop, so the chance of recording one
+    // call site instead of two is about 2*e^-25. The interval also has to stay
+    // above the 131072 bytes that a 100000 byte request actually allocates, so
+    // that sample_size() accounts each sample as one full interval and the
+    // size == count * sample_rate check below holds.
+    std::size_t sample_rate = 200000;
+
+    seastar::memory::set_heap_profiling_sampling_rate(sample_rate);
 
 #ifdef __clang__
     #pragma nounroll
@@ -690,10 +707,10 @@ SEASTAR_TEST_CASE(test_sampled_profile_collection_large)
     {
         auto stats = seastar::memory::sampled_memory_profile();
         BOOST_REQUIRE_EQUAL(stats.size(), 2);
-        BOOST_REQUIRE_EQUAL(stats[0].size, stats[0].count * 1000000);
+        BOOST_REQUIRE_EQUAL(stats[0].size, stats[0].count * sample_rate);
     }
 
-    seastar::memory::set_heap_profiling_sampling_rate(1000000);
+    seastar::memory::set_heap_profiling_sampling_rate(sample_rate);
 
     for (auto ptr : ptrs) {
         free((void*)ptr);