Question about HMSDK's Target Regions for Monitoring

[JongminKim-KU]

Hello, I'm Jongmin Kim from Korea University.

I have a few questions about HMSDK's target regions for monitoring.

I understand that a few essential features of DAMON are as follows:

• DAMON monitors one page per region at every "sampling interval" [1].
• DAMON merges and splits regions with similar access frequencies at every "aggregate interval" [2].
• DAMON supports these features for virtual address space but not for physical address space [3].

Meanwhile, thanks to a convenient tool provided by HMSDKv2.0, users can generate a JSON or YAML file that specifies the target regions of physical address space for DAMON to monitor. I understand that the target regions are configured per node, meaning they encompass a large physical address space. SK hynix announced that HMSDKv2.0 supports merging and splitting regions [4].

So, here are my questions:

1. Does HMSDKv2.0 monitor physical address space? (In other words, do I understand this correctly?)
2. If so, does HMSDKv2.0 support merging and splitting regions of physical address space? (In other words, does HMSDKv2.0 allow DAMON to monitor one page from a single region, or multiple pages from multiple regions?)

I would appreciate it if you could clarify any parts that I have misunderstood.

[1] https://docs.kernel.org/mm/damon/design.html#monitoring [2] https://docs.kernel.org/mm/damon/design.html#adaptive-regions-adjustment [3] https://docs.kernel.org/admin-guide/mm/damon/usage.html#initial-monitoring-target-regions [4] https://youtu.be/K7iHE-vvrRY?si=rnMrGfXzUed63DYm&t=920

[hyeongtakji]

Hello Jongmin,

DAMON supports these features for virtual address space but not for physical address space [3]

I haven't used the "Initial Monitoring Target Regions" feature before, and I noticed that the link says it has been deprecated. However, the sampling, merging, and splitting mechanisms work regardless of whether the target is virtual or physical. FYI, HMSDK v2.0 introduces new DAMOS actions but does not alter the core mechanism of DAMON.

Does HMSDKv2.0 monitor physical address space?

Yes.

If so, does HMSDKv2.0 support merging and splitting regions of physical address space?

Technically yes, since DAMON supports merging and splitting regions of physical address space, and HMSDK v2.0 does not change the core mechanism of DAMON.

[JongminKim-KU]

Thank you for your clear explanation. It is really helpful!