Re: [PATCH v7 0/7] mm: Hot page tracking and promotion infrastructure

Bharata B Rao
2026-05-04T06:23:32Z

On 04-May-26 11:39 AM, Bharata B Rao wrote:
>
> Results
> =======
> Posted as replies to this mail thread.

Micro-benchmark numbers for IBS Memory Profiler pghot source

Test system details
-------------------
2 node AMD system with 1 regular NUMA node (0) and a CXL node (1)

$ numactl -H
available: 3 nodes (0-1)
node 0 cpus: 0-255
node 0 size: 515563 MB
node 1 cpus:
node 1 size: 258034 MB
node distances:
node distances:
node 0 1
0: 10 50
1: 255 10

Hotness sources
---------------
NUMAB0 - Without NUMA Balancing in base case and with no source enabled
in the patched case. No migrations occur.
NUMAB2 - Existing hot page promotion for the base case
HWHINTS - IBS Memory Profiler as source for pghot

Pghot by default promotes after two accesses but for NUMAB2 source,
promotion is done after one access to match the base behaviour.
(/sys/kernel/debug/pghot/freq_threshold=1)

==============================================================
Scenario 1 - Enough memory in toptier and hence only promotion
==============================================================
Multi-threaded application with 64 threads that access memory(8G) at
4K granularity repetitively and randomly. The number of accesses per
thread and the randomness pattern for each thread are fixed beforehand.
The accesses are divided into stores and loads in the ratio of 50:50.

Benchmark threads run on Node 0, while memory is initially provisioned on
CXL node 1 before the accesses start.

Repetitive accesses results in lowertier pages becoming hot and kmigrated
detecting and migrating them. The benchmark score is the time taken to
finish the accesses in microseconds. The sooner it finishes the better it is.
All the numbers shown below are average of 3 runs.

Time taken (microseconds, lower is better)
---------------------------------------------------------
Source Base Pghot-default
---------------------------------------------------------
NUMAB0 181,393,365 184,331,381
NUMAB2 42,287,528
HWHINTS NA 50,422,862
---------------------------------------------------------

Stats comparision b/n base-NUMAB2 and pghot-default-hwhints
---------------------------------------------------------------------
Base-NUMAB2 Pghot-default-hwhints
---------------------------------------------------------------------
pgpromote_success 2097152 1961087
numa_hint_faults 2358069 0
pghot_recorded_accesses NA 1962696
pghot_recorded_hintfaults NA 0
pghot_recorded_hwhints NA 5532979
hwhint_total_events NA 5532979
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