masaori335 commented on code in PR #13785:
URL: https://github.com/apache/trafficserver/pull/13785#discussion_r4203719065
##########
src/iocore/cache/unit_tests/test_RamCacheCLFUS.cc:
##########
@@ -375,3 +375,20 @@ TEST_CASE("CLFUS compression backends compiled in",
"[cache][ramcache][compress]
#endif
CHECK(compression_cases().size() >= 3);
}
+
+// Guards against PR #11733-style regressions of the CLFUS value metric: the
value density
+// must be computed in floating point. Integer division truncates (hits + 1) /
(size + overhead)
+// to 0 for normal object sizes, zeroing the metric and silently collapsing
CLFUS to FIFO (no
+// promote-on-hit, no clock second chance, no value-based ghost re-admission).
+TEST_CASE("CLFUS value metric is a floating-point density",
"[cache][ramcache][clfus]")
+{
+ constexpr double v_one = RamCacheCLFUS::cache_value_hits_size(1u, 16384u);
// a typical 16 KiB object, seen once
+ constexpr double v_hot = RamCacheCLFUS::cache_value_hits_size(100u,
16384u); // same size, many more hits
+ constexpr double v_small = RamCacheCLFUS::cache_value_hits_size(10u, 1024u);
// smaller object, equal hits
+ constexpr double v_large = RamCacheCLFUS::cache_value_hits_size(10u, 16384u);
+
+ // A non-zero fraction: the integer-division regression makes this exactly
0.0.
+ STATIC_REQUIRE(v_one > 0.0);
Review Comment:
Fixed by
[da253b2](https://github.com/apache/trafficserver/pull/13785/commits/da253b2909512c6af0b851bda3b6a2140d82bb31).
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