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b=FeuRPQJ9Z1hQiM6FBo18cOIRE273ysx1hBehJhqIktYMs+f95n7Jn+/CjoMpT4ytg NV8IFu+OY1apecMCxcLKCkGV/J72nrRF/sGC59q7YWv4U9FpJx+W6DMrvUpvXo77zQ DzmzIClz5VZ2kVdAPGkRcTVJ+gH2yv+1vw6t8hZ1obONW2bb0C3C4ZnN4sihR24e3m 9StYOlcWsVG13pKsgKRp5IFtNLHjg37oJ0Tw1LT9CKrZWkjFQShnVQ+JwqWEum8qhU OpefCTD5aSL3yUw5pnL+ny6WBW0Dk93FpoY2U0tkPEdBf0hutHx2Me+lcH0ld+hEjn ymHkEmFN3lAfw== From: SeongJae Park To: Yunjeong Mun Cc: SeongJae Park , akpm@linux-foundation.org, damon@lists.linux.dev, linux-mm@kvack.org, linux-kernel@vger.kernel.org, kernel_team@skhynix.com, honggyu.kim@sk.com Subject: Re: [RFC PATCH 2/2] samples/damon: add `migrate_hot` and `migrate_cold` knobs Date: Tue, 1 Jul 2025 17:08:25 -0700 Message-Id: <20250702000825.57587-1-sj@kernel.org> X-Mailer: git-send-email 2.39.5 In-Reply-To: <20250701085417.1734-3-yunjeong.mun@sk.com> References: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Rspam-User: X-Rspamd-Server: rspam06 X-Rspamd-Queue-Id: 8356FA0005 X-Stat-Signature: 48e6x6rp7izdw3xgebo83gneby5ub3oj X-HE-Tag: 1751414908-355999 X-HE-Meta: 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 JqnnYlda 0jOBUX9U1b4BAXbj8Jzg/9XCHJZ9YQJfdY2OrVSlarjvfIAiTJ0oEf7lz52DFR5gUJYkyDBzIOQ+Yr+biz6q2s43hjrFIOPu5yzmbroCyozPM5HMRHMLnpqehtrGf/xhWstYy8YFTsIOjax6cdqKOmKsMfHG4hbxDNY2cI1/6c9kaRtJSxNbTBCxOvzWKZCp6eTYbhRsK8BiHEr1FWUtZ/UVd/stA7wP/r1rXHcTYeOit80Lg3FywVNAlR/8eM9usiPQGUetOayPgCmJtfx+lOumzvqNKVzre68fdDegxIwaVN8GCkhadCL+nmw== 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: Hello Yunjeong, On Tue, 1 Jul 2025 17:54:17 +0900 Yunjeong Mun wrote: > This patch introduces two new konbs for promotion/demotion: > `migrate_hot` and `migrate_cold`. It receives node ids for migration in > a comma-separated format as ``. The usage is as follows: > > # demote pages from nid 0 to nid 1 > $ echo 0,1 > /sys/module/mtier/parameters/migrate_cold > # promote pages from nid 1 to nid 0 > $ echo 1,0 > /sys/module/mtier/parameters/migrate_hot I understand you want to support some setups such as having a fast node of id 1 and a slow node of id 0. Because mtier is a sample code, I think it's primary goal is to help developers know how they can use DAMON API functions for writing kernel code that is required for a situation similar to the sample. Hence the sample should be clean and simple enough to be understood. The assumption of the two nodes (the fast node 0 and the slow node 1) is arguably intended for making the code simple, in my opinion. We could of course make this kind of changes if it helps more experiments for understanding the code, as sample code is not only for reading but also running. > > Susggested-by: Honggyu Kim checkpatch.pl found a typo: s/Susggest/Suggest/ > Signed-off-by: Yunjeong Mun > --- > samples/damon/mtier.c | 68 +++++++++++++++++++++++++++++++++++++++++-- > 1 file changed, 66 insertions(+), 2 deletions(-) But, I feel like this change is rather making code too longer and complicated. Hence I would suggest dropping this patch if you agree. Please let me know if you have different opinions, or I'm missing something. Thanks, SJ [...]