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bh=iWpeYViYVT9Q3c2NgGbuKH0/3JN3NmmA/uSOtQHdCBw=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=kEUHIbNzVacKEiIWE3We6lJnjqsAO2iEPZyWGmwRfasxmn2EEiqxpCGfYxsBecrMp nnOEZLjFdAzwPFNArr6FPy7H0mi+m7yURLGxbEx1fQG7gaK0L3i/pPdKAZFk/Z4rtQ HKpmlTsTh5vIk3mEklgcyzNgydLmZp/kQ7LEjtNj7WXANxBbrM1jVFzfmEWVcTUh3w uRswj1U6SCfqKAq3GXF0lBHAUT8ltxMjGJtCEoXYYzDH6NOUSAt/Pa/5IH6bccrO5A HFyKMD36Xn4S3ocVjN1HL1UGu+CI039D1c3XLAQ0q8CfYOdI4w4wfQzyEhKnPHCZu4 rj8P8ntWDkbWw== From: SeongJae Park To: Quanmin Yan Cc: SeongJae Park , akpm@linux-foundation.org, damon@lists.linux.dev, linux-kernel@vger.kernel.org, linux-mm@kvack.org, wangkefeng.wang@huawei.com, zuoze1@huawei.com Subject: Re: [PATCH] mm/damon: add a min_sz_region parameter to damon_set_region_biggest_system_ram_default() Date: Thu, 16 Oct 2025 12:48:50 -0700 Message-ID: <20251016194851.65981-1-sj@kernel.org> X-Mailer: git-send-email 2.47.3 In-Reply-To: <20251016104717.2194909-1-yanquanmin1@huawei.com> References: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Rspam-User: X-Stat-Signature: hezxqmy5jrk8gq1gbg8q8gzx8uni71pn X-Rspamd-Queue-Id: DDD98180008 X-Rspamd-Server: rspam09 X-HE-Tag: 1760644140-956401 X-HE-Meta: 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 7MH5n0Bs 0/Al18YYkSPrNeqxKh1l7//XuJ/3Ivh7C/QAOrSOt8WNjSfHkvG3AcDZYmR6QebDIr0Z1ejmqoZ6tUADBbtG6j0/J0WzMLe84zVdBFtpEKGUZGhp2gUcnLWS9Uk4OjMHTxRLNn+QYNipQ6EDRFk5wXwR028anc0L74RTGcZJoDfiSwIM4Ft6+kMLpeEpXjsXLSkxloS26r8Ol+hTDdQM95iA/fByfv1f3GLDCFlClZh55bl5+RIIQ2yoELN6c5ZOJxlMZMXdmAMd0l5DOw4IqISiDWA== X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Thu, 16 Oct 2025 18:47:17 +0800 Quanmin Yan wrote: > After adding addr_unit support for DAMON_LRU_SORT and DAMON_RECLAIM, > the related region setup now requires alignment based on min_sz_region. > > Add min_sz_region to damon_set_region_biggest_system_ram_default() > and use it when calling damon_set_regions(), replacing the previously > hardcoded DAMON_MIN_REGION. Can we add more detailed description of the end user issue on the commit message? My understanding of the issue is that the monitoring target address ranges for DAMON_LRU_SORT and DAMON_RECLAIM would be aligned on DAMON_MIN_REGION * addr_unit. For example, if user sets the monitoring target address range as [4, 8) and addr_unit as 1024, the aimed monitoring target address range is [4 KiB, 8 KiB). But damon_set_regions() will apply DAMON_MIN_REGION as the core address alignment. 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. So the end user effect is that DAMON_LRU_SORT and DAMON_RECLAIM could work for unexpectedly large physical address ranges, when they 1) set addr_unit to a value larger than 1, and 2) set the monitoring target address range as not aligned in 4096*addr_unit. Let me know if I'm misunderstanding something. Also, if you encountered the issue in a real or a realistic use case, adding that on the commit message together would be very helpful. > > Fixes: 2e0fe9245d6b ("mm/damon/lru_sort: support addr_unit for DAMON_LRU_SORT") > Fixes: 7db551fcfb2a ("mm/damon/reclaim: support addr_unit for DAMON_RECLAIM") Let's break this patch into two patches, so that we have one fix per broken commit. > Signed-off-by: Quanmin Yan > --- > include/linux/damon.h | 3 ++- > mm/damon/core.c | 6 ++++-- > mm/damon/lru_sort.c | 3 ++- > mm/damon/reclaim.c | 3 ++- > mm/damon/stat.c | 3 ++- > 5 files changed, 12 insertions(+), 6 deletions(-) The code change looks good to me. Thanks, SJ