Re: [RFC PATCH v5 00/10] mm: Hot page tracking and promotion infrastructure

[Bharata B Rao <bharata@amd.com>]

On 11-Feb-26 9:00 PM, Bharata B Rao wrote:
> On 29-Jan-26 8:10 PM, Bharata B Rao wrote:
>>
>> Results
>> =======
>> TODO: Will post benchmark nubmers as reply to this patchset soon.
> 
> Here are Graph500 numbers for the hint fault source:
> 
> Test system details
> -------------------
> 3 node AMD Zen5 system with 2 regular NUMA nodes (0, 1) and a CXL node (2)
> 
> $ numactl -H
> available: 3 nodes (0-2)
> node 0 cpus: 0-95,192-287
> node 0 size: 128460 MB
> node 1 cpus: 96-191,288-383
> node 1 size: 128893 MB
> node 2 cpus:
> node 2 size: 257993 MB
> node distances:
> node   0   1   2
>   0:  10  32  50
>   1:  32  10  60
>   2:  255  255  10
> 
> Hotness sources
> ---------------
> NUMAB0 - Without NUMA Balancing in base case and with no source enabled
>          in the pghot case. No migrations occur.
> NUMAB2 - Existing hot page promotion for the base case and
>          use of hint faults as source in the pghot case.
> 
> 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)
> 

These numbers are from scenario where demotion is present:

=============================================
Over-committed scenario, promotion + demotion
=============================================
Command: mpirun -n 128 --bind-to core --map-by core
/home/bharata/benchmarks/graph500/src/graph500_reference_bfs 30 16

The scale factor of 30 results in around 400GB of memory being
provisioned resulting in the data spilling over to CXL node.
No explicit migration of data is done in this case unlike the
previous case.

=====================================================================================
                        Base            Base            pghot-default
pghot-precise
                        NUMAB0          NUMAB2          NUMAB2          NUMAB2
=====================================================================================
harmonic_mean_TEPS      9.28713e+08     7.90431e+08     7.32193e+08     7.81051e+08
mean_time               18.4984         21.7346         23.4634         21.9956
median_TEPS             9.25707e+08     7.86684e+08     7.27053e+08     7.82823e+08
max_TEPS                9.57632e+08     8.4758e+08      8.22172e+08     7.9889e+08

pgpromote_success       0               22846743        22807167        25994988
pgpromote_candidate     0               24628924        29436044        27029173
pgpromote_candidate_nrl 0               140921          220             38387
pgdemote_kswapd         0               41523110        45121134        50042594
numa_pte_updates        0               121904763       71503891        68779424
numa_hint_faults        0               81708126        29583391        27176332
=====================================================================================

- In the base case, the benchmark suffers when promotion and demotion are
  enabled (NUMAB2 case).
- Same behaviour is seen with both modes of pghot.
- Though the overall benchmark numbers remain more or less same with base and
  pghot NUMAB2 cases, the number of pte updates and hint faults are seen
  to spike up during some runs. Yet to understand the exact reason for this.