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Wed, 4 Feb 2026 16:07:40 +0300 Message-ID: <8b8e9dde-33ff-41f7-8563-d9aeaf5efeb5@huawei-partners.com> Date: Wed, 4 Feb 2026 16:07:40 +0300 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [RFC PATCH v1 0/4] mm/damon: Support hot application detections To: SeongJae Park CC: , , , , , , , , References: <20260204071712.16325-1-sj@kernel.org> Content-Language: en-US From: Gutierrez Asier In-Reply-To: <20260204071712.16325-1-sj@kernel.org> Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: 7bit X-Originating-IP: [10.123.123.154] X-ClientProxiedBy: mscpeml100003.china.huawei.com (10.199.174.67) To mscpeml500003.china.huawei.com (7.188.49.51) X-Rspamd-Server: rspam12 X-Stat-Signature: wyi75td8oa8d7nwuy4o8wyisemsuc3nz X-Rspamd-Queue-Id: 3A5CAC0002 X-Rspam-User: X-HE-Tag: 1770210466-700287 X-HE-Meta: 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 rjdUgh3C R5znSdDsmEKnZ/XDzW+A5vrRI/IcSZ9XlIao/xjODCYheFED1wYWKOD4xfRLEe7bMTetbd3ZPhJg+z8troNfDspOixT4Zr+0iPOLRq9tWToVZlvU/ItuoKC8loEsjuqbCIZeBt+JFZbbE/H0THQfFNqvMcHm0350qoPDwHN2SA1YvdzlCjX1l7C2z6k/SrRaWVaP2DWV72T4UXerBNf0TCsu6b6Sbcfne+39Jyqdfexu33JYGa6xRG/yTMPlEv6zBLglpShtGIkH10Xqgda7hn9gq8g== X-Bogosity: Ham, tests=bogofilter, spamicity=0.000376, 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 2/4/2026 10:17 AM, SeongJae Park wrote: > On Tue, 3 Feb 2026 17:25:11 +0300 Gutierrez Asier wrote: > >> SeongJae, >> >> Thanks a lot for all the useful feedback. > > The pleasure is mine! :) > >> >> One thing that I was not sure about while working on this patch set >> is whether to have an external new module or adding the logic to >> damon core. I mean, the hot application detecting can be useful for >> all other modules and can improve DAMON performance. > > All exising non-sample DAMON modules are working for the physical address > space. I hence finding no many opportunities to bring benefits of hot > application detection to those. > > I agree the hot applications detection could be useful in general and creative > DAMON use cases for virtual address spaces. Implementing the feature in DAMON > core layer and exposing it via DAMON sysfs interface will help such use cases. > But it seems not straightforward to imagine how the sysfs interface can be > extended for the feature. > > So, I think it would better to be implemented inside the new module at the > moment. Later, if we end up having more modules that use the feature, we could > move it to the modules-common or the core. If we further find a good way to > integrate that with sysfs interface, definitely it could go to core. > > From this point, however, I realize the feature can also be implemented in the > user sapce in a pretty straightforward way. Have you considered that? I though about it. However, accessing the task_struct directly and extracting the utime is much more efficient that getting the required info from the user space. > >> What do you think? >> My implementation was module based because I tried to avoid changes >> to DAMON core for the RFC. > > If there is a good reason to implement that not in the user space but the > kernel space, as I mentioned above, it seems the module is the right place to > me. > > > Thanks, > SJ > > [...] > -- Asier Gutierrez Huawei