linux-kernel - Re: [PATCH v2 1/2] mm/damon: add a min_sz_region parameter to damon_set_region_biggest_system_ram

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Message-ID: <20251020150658.39741-1-sj@kernel.org>
Date: Mon, 20 Oct 2025 08:06:58 -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: [PATCH v2 1/2] mm/damon: add a min_sz_region parameter to damon_set_region_biggest_system_ram_default()

On Mon, 20 Oct 2025 21:01:24 +0800 Quanmin Yan <yanquanmin1@...wei.com> wrote:

> In DAMON_LRU_SORT, damon_set_regions() will apply DAMON_MIN_REGION as
> the core address alignment, and the monitoring target address ranges
> would be aligned on DAMON_MIN_REGION * addr_unit. When users 1) set
> addr_unit to a value larger than 1, and 2) set the monitoring target
> address range as not aligned on DAMON_MIN_REGION * addr_unit, it will
> cause DAMON_LRU_SORT to operate on unexpectedly large physical address
> ranges.
> 
> For example, if the user sets the monitoring target address range to
> [4, 8) and addr_unit as 1024, the aimed monitoring target address range
> is [4 KiB, 8 KiB). Assuming DAMON_MIN_REGION is 4096, so resulting
> target address range will be [0, 4096) in the DAMON core layer address
> system, and [0, 4 MiB) in the physical address space, which is an
> unexpected range.
> 
> To fix the issue, add a min_sz_region parameter to
> damon_set_region_biggest_system_ram_default() and use it when calling
> damon_set_regions(), replacing the direct use of DAMON_MIN_REGION.
> 
> Fixes: 2e0fe9245d6b ("mm/damon/lru_sort: support addr_unit for DAMON_LRU_SORT")
> Signed-off-by: Quanmin Yan <yanquanmin1@...wei.com>

Reviewed-by: SeongJae Park <sj@...nel.org>


Thanks,
SJ

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