Re: [PATCH v4] mm,memcg: provide per-cgroup counters for NUMA balancing operations

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On Wed, 14 Aug 2024 23:51:22 +0000 kaiyang2@xxxxxxxxxx wrote:

> From: Kaiyang Zhao <kaiyang2@xxxxxxxxxx>
> 
> The ability to observe the demotion and promotion decisions made by the
> kernel on a per-cgroup basis is important for monitoring and tuning
> containerized workloads on machines equipped with tiered memory.
> 
> Different containers in the system may experience drastically different
> memory tiering actions that cannot be distinguished from the global
> counters alone.
> 
> For example, a container running a workload that has a much hotter
> memory accesses will likely see more promotions and fewer demotions,
> potentially depriving a colocated container of top tier memory to such
> an extent that its performance degrades unacceptably.
> 
> For another example, some containers may exhibit longer periods between
> data reuse, causing much more numa_hint_faults than numa_pages_migrated.
> In this case, tuning hot_threshold_ms may be appropriate, but the signal
> can easily be lost if only global counters are available.
> 
> In the long term, we hope to introduce per-cgroup control of promotion
> and demotion actions to implement memory placement policies in tiering.
> 
> This patch set adds seven counters to memory.stat in a cgroup:
> numa_pages_migrated, numa_pte_updates, numa_hint_faults, pgdemote_kswapd,
> pgdemote_khugepaged, pgdemote_direct and pgpromote_success. pgdemote_*
> and pgpromote_success are also available in memory.numa_stat.
> 
> count_memcg_events_mm() is added to count multiple event occurrences at
> once, and get_mem_cgroup_from_folio() is added because we need to get a
> reference to the memcg of a folio before it's migrated to track
> numa_pages_migrated. The accounting of PGDEMOTE_* is moved to
> shrink_inactive_list() before being changed to per-cgroup.

There appears to have been little reviewer interest in this one?




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