| Message ID | 20231205022858.1540-1-sj@kernel.org (mailing list archive) |
|---|---|
| Headers | show |
| Series | mm/damon: export DAMON symbols and add sample loadable modules | expand |
On Tue, Dec 05, 2023 at 02:28:55AM +0000, SeongJae Park wrote: > DAMON cannot be used from loadable modules since it is not exporting its > symbols. And that is a good thing. We should absolutely not allow random modules probing MM internals. What you posted here is basically just adding hooks without even real in-kernel users.
Hi Christoph, On 2023-12-04T21:12:47-08:00 Christoph Hellwig <hch@infradead.org> wrote: > On Tue, Dec 05, 2023 at 02:28:55AM +0000, SeongJae Park wrote: > > DAMON cannot be used from loadable modules since it is not exporting its > > symbols. > > And that is a good thing. We should absolutely not allow random modules > probing MM internals. I agree. > What you posted here is basically just adding hooks without even real > in-kernel users. I was thinking someone might be able to think even the sample module as real usage since there was actually some questions about it from real users. That said, those were more like questions than strong requests, so I still think this change is somewhat better to be made for at least some folks, but I also agree that this wouldn't be not really essential for everyone, and could be only long term maintenance threat. I personally don't have strong opinion, and thank you for raising your concern. I will hold this patchset unless someone request this change again with good rationale. Btw, I know there were many concerns about unnecessarily exporting symbols, but do we have a formal guideline or documentation about the requirements for exporting symbols in sepcific subsystem? I was hoping to have such one so that I could provide better answer to DAMON's loadable module support questions, but I was unable to find such one with my poor searching skill. This reply could be used for the purpose meanwhile, though, so appreciate again. :) Thanks, SJ
Changes from RFC (https://lore.kernel.org/damon/20231121053604.60798-1-sj@kernel.org/) - Wordsmith commit message - Use GPL v2 for Makefile - Separate patch for each sample module DAMON cannot be used from loadable modules since it is not exporting its symbols. This makes use of DAMON unnecessarily tedious. For example, basic usage of DAMON was presented at kernel summit 2021[1] by writing simple loadable DAMON application modules in live. Because the time was limited (10 minutes) and the coding was to be done step by step, it had to make a downstream commit that exports DAMON symbols. There were users asking why the source code is now not working. It was mainly due to the absence of the symbols export patch on their tree, but also due to the updated DAMON programming interfaces. There were also multiple users requesting support of loadable modules for easier deployment. There's no reason to avoid exporting DAMON symbols. However, it would be better to have concrete use cases of the symbols in the tree together, for better maintenance of the interface and the use cases. The kernels summit 2021's live-coded modules could be used for the purpose. Expose DAMON API modules for supporting the minimum modules and add the kernel summit 2021's modules that updated for latest DAMON API under the samples directory. The sample modules will be keep updated. For exporting more symbols, requesters would be required to merge their modules using the symbols in the tree together, or updsate the sample modules to use the newly-exporting symbols in still simple but reasonable ways. [1] https://linuxplumbersconf.org/event/11/contributions/984/ Signed-off-by: SeongJae Park <sj@kernel.org> SeongJae Park (3): mm/damon/core: export symbols for supporting loadable modules samples: add working set size estimation DAMON sample module samples: add proactive reclamation DAMON sample module MAINTAINERS | 1 + mm/damon/core.c | 10 +++ samples/Kconfig | 2 + samples/Makefile | 2 + samples/damon/Kconfig | 30 +++++++++ samples/damon/Makefile | 3 + samples/damon/damon_sample_prcl.c | 102 ++++++++++++++++++++++++++++++ samples/damon/damon_sample_wsse.c | 85 +++++++++++++++++++++++++ 8 files changed, 235 insertions(+) create mode 100644 samples/damon/Kconfig create mode 100644 samples/damon/Makefile create mode 100644 samples/damon/damon_sample_prcl.c create mode 100644 samples/damon/damon_sample_wsse.c base-commit: 7fcebba4a540e4508b923f00a3e9c5e4710f147f