Re: [PATCH 0/7] mm/damon/reclaim,lru_sort: monitor all system rams by default

SeongJae Park
2026-04-29T14:30:57Z

On Tue, 28 Apr 2026 21:12:22 -0700 SeongJae Park <sj@kernel.org> wrote:

> DAMON_RECLAIM and DAMON_LRU_SORT set the biggest 'System RAM' resource
> of the system as the default monitoring target address range. The main
> intention behind the design is to minimize the overhead coming from
> monitoring of non-System RAM areas.
>
> This could result in an odd setup when there are multiple discrete
> System RAMs of considerable sizes. For example, there are System RAMs
> each having 500 GiB size. In this case, only the first 500 GiB will be
> set as the monitoring region by default. This is particularly common on
> NUMA systems. Hence the modules allow users to set the monitoring
> target address range using the module parameters if the default setup
> doesn't work for them. In other words, the current design trades ease
> of setup for lower overhead.
>
> However, because DAMON utilizes the sampling based access check and the
> adaptive regions adjustment mechanisms, the overhead from the monitoring
> of non-System RAM areas should be negligible in most setups. Meanwhile,
> the setup complexity is causing real headaches for users who need to run
> those modules on various types of systems. That is, the current
> tradeoff is not a good deal.
>
> Set the physical address range that can cover all System RAM areas of
> the system as the default monitoring regions for DAMON_RECLAIM and
> DAMON_LRU_SORT.

FYI, Sashiko reviews and my review of the reviews are available on replies to
this thread that Cc-ing only me and damon@lists.linux.dev
(https://lore.kernel.org/20260429041232.90257-1-sj@kernel.org). In short, no
real issue that blocks this series is found by Sashiko.

Thanks,
SJ …