Re: [PATCH linux-next v3 0/6] memcg: Support per-memcg KSM metrics

[David Hildenbrand]

On 21.09.25 17:07, xu.xin16@xxxxxxxxxx wrote:
> From: xu xin <xu.xin16@xxxxxxxxxx>
>
> v2->v3:
> ------
> Some fixes of compilation error due to missed inclusion of header or missed
> function definition on some kernel config.
> https://lore.kernel.org/all/202509142147.WQI0impC-lkp@xxxxxxxxx/
> https://lore.kernel.org/all/202509142046.QatEaTQV-lkp@xxxxxxxxx/
>
> v1->v2:
> ------
> According to Shakeel's suggestion, expose these metric item into memory.stat
> instead of a new interface.
> https://lore.kernel.org/all/ir2s6sqi6hrbz7ghmfngbif6fbgmswhqdljlntesurfl2xvmmv@yp3w2lqyipb5/
>
> Background
> ==========
>
> With the enablement of container-level KSM (e.g., via prctl [1]), there is
> a growing demand for container-level observability of KSM behavior. However,
> current cgroup implementations lack support for exposing KSM-related metrics.
>
> So add the counter in the existing memory.stat without adding a new interface.
> To diaplay per-memcg KSM statistic counters,  we traverse all processes of a
> memcg and summing the processes' ksm_rmap_items counters instead of adding enum
> item in memcg_stat_item or node_stat_item and updating the corresponding enum
> counter when ksmd manipulate pages.
>
> Now Linux users can look up all per-memcg KSM counters by:
>
> # cat /sys/fs/cgroup/xuxin/memory.stat | grep ksm
> ksm_rmap_items 0
> ksm_zero_pages 0
> ksm_merging_pages 0
> ksm_profit 0


No strong opinion from my side: seems to mostly only collect stats from 
all tasks to summarize them per memcg.

--
Cheers

David / dhildenb