diff --git a/README.md b/README.md
index cabf4ad..f1dc6de 100644
--- a/README.md
+++ b/README.md
@@ -43,6 +43,7 @@ mkdir -p "${KV_BENCH_STORAGE_ROOT}/basic_mace" "${KV_BENCH_STORAGE_ROOT}/basic_r
 
 ## What Is Compared
 - Comparison unit: rows with identical `workload_id`, `threads`, `key_size`, `value_size`, `durability_mode`, `read_path`
+- Fairness rule for read-heavy workloads: `get`, `scan`, `mixed`, and `W1`-`W6` run one GC/compaction pass after prefill and before warmup/measurement, so RocksDB is not compared with GC artificially disabled while reads may have to touch multiple SSTs
 - Throughput metric: workload-level `ops_per_sec` (higher is better)
   - `W1/W2/W3/W4`: mixed read+update throughput
   - `W5`: mixed read+update+scan throughput
diff --git a/docs/repro.md b/docs/repro.md
index 31ffeee..073288b 100644
--- a/docs/repro.md
+++ b/docs/repro.md
@@ -63,6 +63,10 @@ WARMUP_SECS=3 MEASURE_SECS=5 PREFILL_KEYS=50000 \
 ./scripts/rocksdb.sh "${KV_BENCH_STORAGE_ROOT}/basic_rocks" "${KV_BENCH_RESULT_ROOT}/benchmark_results.csv"
 ```
 
+Fairness note:
+- For read-heavy workloads (`get`, `scan`, `mixed`, and `W1`-`W6`), both harnesses run one GC/compaction pass after prefill and before warmup/measurement.
+- The purpose is to make the RocksDB vs Mace comparison fairer, since RocksDB reads may need to touch multiple SSTs and should not be benchmarked with GC/compaction artificially disabled.
+
 Generate plots:
 
 ```bash
@@ -202,5 +206,6 @@ Only compare rows with identical:
 - `threads`
 - `durability_mode`
 - `read_path`
+- read-heavy workload rows are expected to include the pre-run GC/compaction pass described above
 
 If `error_ops > 0`, investigate that case before drawing conclusions.
diff --git a/rocksdb/main.cpp b/rocksdb/main.cpp
index 0df0aed..1310bc0 100644
--- a/rocksdb/main.cpp
+++ b/rocksdb/main.cpp
@@ -289,6 +289,22 @@ static std::optional<WorkloadSpec> parse_workload(const Args &args, std::string
     return std::nullopt;
 }
 
+static bool workload_runs_gc(const WorkloadSpec &spec) {
+    return spec.requires_prefill;
+}
+
+static void run_prefill_gc(rocksdb::OptimisticTransactionDB *db,
+                           rocksdb::ColumnFamilyHandle *handle) {
+    require_ok(db->EnableAutoCompaction({handle}), "enable auto compaction");
+
+    rocksdb::FlushOptions flush_options;
+    flush_options.wait = true;
+    require_ok(db->Flush(flush_options, handle), "prefill flush");
+
+    rocksdb::CompactRangeOptions compact_options;
+    require_ok(db->CompactRange(compact_options, handle, nullptr, nullptr), "prefill compaction");
+}
+
 static std::vector<ThreadRange> split_ranges(size_t total, size_t n) {
     std::vector<ThreadRange> out;
     out.reserve(n);
@@ -801,10 +817,6 @@ int main(int argc, char *argv[]) {
     cfo.enable_blob_files = true;
     cfo.min_blob_size = args.blob_size;
     cfo.disable_auto_compactions = true;
-    cfo.max_compaction_bytes = (1ULL << 60);
-    cfo.level0_stop_writes_trigger = 1000000;
-    cfo.level0_slowdown_writes_trigger = 1000000;
-    cfo.level0_file_num_compaction_trigger = 1000000;
     cfo.write_buffer_size = 64 << 20;
     cfo.max_write_buffer_number = 128;
 
@@ -822,6 +834,7 @@ int main(int argc, char *argv[]) {
     options.enable_pipelined_write = true;
     options.max_background_flushes = 8;
     options.env->SetBackgroundThreads(8, rocksdb::Env::Priority::HIGH);
+    options.env->SetBackgroundThreads(8, rocksdb::Env::Priority::LOW);
 
     auto wopt = rocksdb::WriteOptions();
     wopt.no_slowdown = true;
@@ -871,6 +884,10 @@ int main(int argc, char *argv[]) {
         }
     }
 
+    if (workload_runs_gc(workload_spec)) {
+        run_prefill_gc(db, handle);
+    }
+
     std::barrier ready_barrier(static_cast<ptrdiff_t>(args.threads + 1));
     std::barrier measure_barrier(static_cast<ptrdiff_t>(args.threads + 1));
 
diff --git a/scripts/fast_test.py b/scripts/fast_test.py
index 942b8a2..d922610 100644
--- a/scripts/fast_test.py
+++ b/scripts/fast_test.py
@@ -144,7 +144,7 @@ def run_engine_cases(
                     f"[run] engine={engine} mode={mode_display} "
                     f"threads={threads} key={key_size} value={value_size}"
                 )
-                print(f"{' '.join(args)}")
+                # print(f"{' '.join(args)}")
                 subprocess.run(args, check=True)
 
 
diff --git a/src/main.rs b/src/main.rs
index e91a005..e93a06c 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -378,6 +378,10 @@ fn parse_workload(args: &Args) -> Result<WorkloadSpec, String> {
     }
 }
 
+fn workload_runs_gc(spec: &WorkloadSpec) -> bool {
+    spec.requires_prefill
+}
+
 fn split_ranges(total: usize, n: usize) -> Vec<ThreadRange> {
     let mut ranges = Vec::with_capacity(n);
     if n == 0 {
@@ -775,6 +779,11 @@ fn main() {
         }
     }
 
+    if workload_runs_gc(&workload) {
+        db.enable_gc();
+        db.start_gc();
+    }
+
     let op_counts = split_ranges(args.iterations, args.threads);
     let ready_barrier = Arc::new(Barrier::new(args.threads + 1));
     let measure_barrier = Arc::new(Barrier::new(args.threads + 1));