Re: [PATCH 0/6] sched/numa: Complete scanning of partial and inactive VMAs

[Raghavendra K T]

On 10/10/2023 2:01 PM, Mel Gorman wrote:
> NUMA Balancing currently uses PID fault activity within a VMA to
> determine if it is worth updating PTEs to trap NUMA hinting faults.
> While this is reduces overhead, it misses two important corner case.
> The first is that if Task A partially scans a VMA that is active and
> Task B resumes the scan but is inactive, then the remainder of the VMA
> may be missed. Similarly, if a VMA is inactive for a period of time then
> it may never be scanned again.
>
> Patches 1-3 improve the documentation of the current per-VMA tracking
> and adds a trace point for scan activity. Patch 4 addresses a corner
> case where the PID activity information may not be reset after the
> expected timeout. Patches 5-6 complete the scanning of partial and
> inactive VMAs within the scan sequence.
>
> This could be improved further but it would deserve a separate series on
> top with supporting data justifying the change. Otherwise and gain/loss
> due to the additional changes could be masked by this series on its own.

Thank you Mel for the patches. I see Ingo already took to sched/core.
Here is my testing detail FWIW.

SUT:
- 4th Generation EPYC System
- 2 x 128C/256T
- NPS1 mode

base: 6.6.-rc4
patch_v1r5: Mel's  Initial series with prev_scan_seq = -1 fix
 Link: https://git.kernel.org/pub/scm/linux/kernel/git/mel/linux.git/ 
sched-numabselective-v1r5

(May not be relevant. But I did see number was even more better for
thread_alloc, so ..)

patch_v1_r13: current series

numa01_thread_alloc
=============
        base            patch_v1r5      patch_v1r13

real    8m46.557s       8m29.040s       8m38.098s
user    599m6.070s      268m38.140s     404m52.065s
sys     3655m38.681s    3794m10.079s    3751m36.779s

numa_hit                394964680       396000482       393981391
numa_local              197351688       198242761       197008099
numa_other              197612992       197757721       196973292
numa_pte_updates        1160            790360          812
numa_hint_faults        755             729196          553
numa_hint_faults_local  754             410220          263
numa_pages_migrated     1               318976          290

num01
======

real    18m26.691s      17m31.770s      17m33.540s
user    4501m40.194s    2148m7.993s     3295m57.897s
sys     3483m11.684s    4764m57.876s    4215m35.599s

numa_hit                395473956       395813242        395000242
numa_local              197776626       198188480        197983594
numa_other              197697330       197624762        197016648
numa_pte_updates        1447            4625319          7142774
numa_hint_faults        1390            4947832          10313097
numa_hint_faults_local  1288            2758651          5354895
numa_pages_migrated     102             594803           960422


Thanks and Regards
- Raghu