On Wed, 17 Jan 2024 13:11:03 -0800 SeongJae Park [off-list ref] wrote:

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Hi Honggyu,

On Wed, 17 Jan 2024 20:49:25 +0900 Honggyu Kim [off-list ref] wrote:

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Hi SeongJae,

Thanks very much for your comments in details.

On Tue, 16 Jan 2024 12:31:59 -0800 SeongJae Park [off-list ref] wrote:

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To this end, I feel the problem might be able te be simpler, because this
patchset is trying to provide two sophisticated operations, while I think a
simpler approach might be possible.  My humble simpler idea is adding a DAMOS
operation for moving pages to a given node (like sys_move_phy_pages RFC[1]),
instead of the promote/demote.  Because the general pages migration can handle
multiple cases including the promote/demote in my humble assumption.

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In more detail, users could decide which is the appropriate node for promotion
or demotion and use the new DAMOS action to do promotion and demotion.  Users
would requested to decide which node is the proper promotion/demotion target
nodes, but that decision wouldn't be that hard in my opinion.

For this, 'struct damos' would need to be updated for such argument-dependent
actions, like 'struct damos_filter' is haing a union.

That might be a better solution.  I will think about it.

More specifically, I think receiving an address range as the argument might
more flexible than just NUMA node.  Maybe we can imagine proactively migrating
cold movable pages from normal zones to movable zones, to avoid normal zone
memory pressure.

Yet another crazy idea.  Finding hot regions in the middle of cold region and
move to besides of other hot pages.  As a result, memory is sorted by access
temperature even in same node, and the system gains more spatial locality,
which benefits general locality-based algorithms including DAMON's adaptive
regions adjustment.


Thanks,
SJ

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