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The measurement phase drives GET traffic with memtier (16 threads x 100 conns, PASSES=12) over 50% of the keyspace so that repeatedly-accessed lower-tier pages become promotion candidates. We compare throughput/latency and the kernel promotion activity across the base kernel and the pghot kernel, and across hotness sources (NUMA- balancing hint faults vs. the IBS hardware memory profiler). System: AMD Zen6, Nodes 0,1 = DRAM (top tier); node 2 = CXL (lower tier). Cases: C1 base/NUMAB0 base kernel, promotion OFF (baseline) C2 base/NUMAB2 base kernel, NUMAB tiering promotion ON C3 pghot/NUMAB2 pghot kernel, promotion via pghot, source = NUMA hint faults (kmigrated batched migration) C4 pghot/IBS-10000 pghot, source = IBS profiler (period 10000), NUMAB=0 C5 pghot/IBS-5000 same as C4 but IBS period=5000 (2x sampling) ========================================================================= Table 1: Benchmark metrics (memtier) ========================================================================= Case NUMAB Ops/sec vs base Avg p50 p99 p99.9 latency (ms) -> ------------------------------------------------------------------------ C1 base/NUMAB0 0 281,424 ref 181.62 180.22 348.16 362.50 C2 base/NUMAB2 2 295,551 +5.0% 173.18 168.96 307.20 354.30 C3 pghot/NUMAB2 2 296,269 +5.3% 172.42 169.98 327.68 364.54 C4 pghot/IBS-10000 0 281,645 +0.1% 181.67 179.20 350.21 362.50 C5 pghot/IBS-5000 0 281,665 +0.1% 181.72 180.22 348.16 362.50 ------------------------------------------------------------------------ ========================================================================= Table 2: Page-migration metrics (vmstat delta over measurement) ========================================================================= Legend: C1=base/NUMAB0 C2=base/NUMAB2 C3=pghot/NUMAB2 C4=pghot/IBS-10000 C5=pghot/IBS-5000 ('-'=counter absent) metric C1 C2 C3 C4 C5 ------------------------------------------------------------------------- pgpromote_success 0 10,433,576 10,433,484 594,762 1,128,469 pgpromote_candidate_nrl 0 10,433,576 10,433,484 594,762 1,128,469 numa_pte_updates 0 20,333,714 20,344,211 0 0 numa_hint_faults 0 10,433,576 10,433,533 0 0 numa_pages_migrated 0 10,433,576 10,433,484 594,762 1,128,463 pgmigrate_success 0 10,433,576 10,433,484 594,762 1,128,463 pghot_recorded_accesses - - 10,433,533 595,426 1,130,753 pghot_recorded_hintfaults - - 10,433,533 0 0 pghot_recorded_hwhints - - 0 1,000,187 2,026,558 pgdemote_kswapd 0 0 0 0 0 ------------------------------------------------------------------------- ========================================================================= Key observations ========================================================================= 1. Promotion helps this workload: enabling NUMAB tiering promotion lifts throughput from 281,424 to 295,551 ops/sec (+5.0%) and cuts average latency 181.6 -> 173.2 ms. 2. pghot-hintfault has no regression vs base as it matches the base tiering case. 3. pghot-hwhint sources promotes far fewer pages than hint faults and it barely shows any improvement over base notier case. 4. Halving the period (10000->5000) ~doubles hw hints (1.00M->2.03M) and promotions (0.59M->1.13M) as expected, but is still far short of the hot set, so throughput does not yet move.