Re: [PATCH v5 0/2] sched/numa: Skip VMA scanning on memory pinned to one NUMA node via cpuset.mems

[K Prateek Nayak]

Hello Libo,

On 4/24/2025 8:15 AM, Libo Chen wrote:
> v1->v2:
> 1. add perf improvment numbers in commit log. Yet to find perf diff on
> will-it-scale, so not included here. Plan to run more workloads.
> 2. add tracepoint.
> 3. To peterz's comment, this will make it impossible to attract tasks to
> those memory just like other VMA skippings. This is the current
> implementation, I think we can improve that in the future, but at the
> moment it's probabaly better to keep it consistent.

I tested the series with hackbench running on a dual socket system with
memory pinned to one node and I could see the skip_cpuset_numa traces
being logged:

 sched-messaging-9430    ...: sched_skip_cpuset_numa: comm=sched-messaging pid=9430 tgid=9007 ngid=0 mem_nodes_allowed=0
 sched-messaging-9640    ...: sched_skip_cpuset_numa: comm=sched-messaging pid=9640 tgid=9007 ngid=0 mem_nodes_allowed=0
 sched-messaging-9645    ...: sched_skip_cpuset_numa: comm=sched-messaging pid=9645 tgid=9007 ngid=0 mem_nodes_allowed=0
 sched-messaging-9637    ...: sched_skip_cpuset_numa: comm=sched-messaging pid=9637 tgid=9007 ngid=0 mem_nodes_allowed=0
 sched-messaging-9629    ...: sched_skip_cpuset_numa: comm=sched-messaging pid=9629 tgid=9007 ngid=0 mem_nodes_allowed=0
 sched-messaging-9639    ...: sched_skip_cpuset_numa: comm=sched-messaging pid=9639 tgid=9007 ngid=0 mem_nodes_allowed=0
 sched-messaging-9630    ...: sched_skip_cpuset_numa: comm=sched-messaging pid=9630 tgid=9007 ngid=0 mem_nodes_allowed=0
 sched-messaging-9487    ...: sched_skip_cpuset_numa: comm=sched-messaging pid=9487 tgid=9007 ngid=0 mem_nodes_allowed=0
 sched-messaging-9635    ...: sched_skip_cpuset_numa: comm=sched-messaging pid=9635 tgid=9007 ngid=0 mem_nodes_allowed=0
 sched-messaging-9647    ...: sched_skip_cpuset_numa: comm=sched-messaging pid=9647 tgid=9007 ngid=0 mem_nodes_allowed=0
 ...

Feel free to add:

Tested-by: K Prateek Nayak <kprateek.nayak@xxxxxxx>

--
Thanks and Regards,
Prateek

> v2->v3:
> 1. add enable_cpuset() based on Mel's suggestion but again I think it's
> redundant.
> 2. print out nodemask with %*p.. format in the tracepoint.
>
> v3->v4:
> 1. fix an unsafe dereference of a pointer to content not on ring buffer,
> namely mem_allowed_ptr in the tracepoint.
>
> v4->v5:
> 1. add BUILD_BUG_ON() in TP_fast_assign() to guard against future
> changes (particularly in size) in nodemask_t.
>
> Libo Chen (2):
>    sched/numa: Skip VMA scanning on memory pinned to one NUMA node via
>      cpuset.mems
>    sched/numa: Add tracepoint that tracks the skipping of numa balancing
>      due to cpuset memory pinning
>
>   include/trace/events/sched.h | 33 +++++++++++++++++++++++++++++++++
>   kernel/sched/fair.c          |  9 +++++++++
>   2 files changed, 42 insertions(+)