linux-kernel - Re: [RFC PATCH mm-next v2 00/12] mm/damon: support ARM32 with LPAE

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Message-Id: <20250820222302.88000-1-sj@kernel.org>
Date: Wed, 20 Aug 2025 15:23:02 -0700
From: SeongJae Park <sj@...nel.org>
To: Quanmin Yan <yanquanmin1@...wei.com>
Cc: SeongJae Park <sj@...nel.org>,
	akpm@...ux-foundation.org,
	damon@...ts.linux.dev,
	linux-kernel@...r.kernel.org,
	linux-mm@...ck.org,
	wangkefeng.wang@...wei.com,
	zuoze1@...wei.com
Subject: Re: [RFC PATCH mm-next v2 00/12] mm/damon: support ARM32 with LPAE

On Wed, 20 Aug 2025 16:06:10 +0800 Quanmin Yan <yanquanmin1@...wei.com> wrote:

> Previously, DAMON's physical address space monitoring only supported
> memory ranges below 4GB on LPAE-enabled systems. This was due to
> the use of 'unsigned long' in 'struct damon_addr_range', which is
> 32-bit on ARM32 even with LPAE enabled[1].
> 
> To add DAMON support for ARM32 with LPAE enabled, a new core layer
> parameter called 'addr_unit' was introduced[2]. Operations set layer
> can translate a core layer address to the real address by multiplying
> the parameter value to the core layer address. Support of the parameter
> is up to each operations layer implementation, though. For example,
> operations set implementations for virtual address space can simply
> ignore the parameter. Add the support on paddr, which is the DAMON
> operations set implementation for the physical address space, as we have
> a clear use case for that.
> 
> [1]https://lore.kernel.org/all/20250408075553.959388-1-zuoze1@huawei.com/
> [2]https://lore.kernel.org/all/20250416042551.158131-1-sj@kernel.org/
> 
> Changes in v2:

It would be nice if you can also add the link to the previous version, e.g.,
like the revisions history of
https://lore.kernel.org/20250819193404.46680-1-sj@kernel.org

> - set DAMOS_PAGEOUT, DAMOS_LRU_[DE]PRIO, DAMOS_MIGRATE_{HOT,COLD} and
>   DAMOS_STAT stat in core address unit.
> - pass ctx->min_region value to replace the original synchronization.
> - drop the DAMOS stats type changes, keep them as 'unsigned long' type.
> - separate add addr_unit support for DAMON_RECLAIM and LRU_SORT from
>   this patch series.

Thank you for continuing this work!

> 
> Quanmin Yan (2):
>   mm/damon: add damon_ctx->min_region
>   mm/damon/core: prevent unnecessary overflow in
>     damos_set_effective_quota()

I left a few comments.  In essense, let's rename min_region to min_sz_region,
and separate the last fix from this series.

Other than above, looks good overall.  I think you can drop RFC tag from the
next version.


Thanks,
SJ

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