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Maintaining DAMON (https://damonitor.github.io). All opinions are my own.
sj

sj

According to LWN, I was [1] 14-th most active developer for Linux v6.17, in terms of the number of changes. Numbers are no more no less just numbers, but being listed there twice [2] means something to me :)

[1] https://lwn.net/Articles/1038358/
[2] https://social.kernel.org/notice/AsT2MVtG6Lv7PONehE

#linux #kernel #damon #lwn
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Reply to @vbabka@mastodon.social
@vbabka @rostedt I wouldn't dare to compete ;) I just had to accept the fact that I was too lazy at sharing and discussing my outputs and crazy ideas, and trying to have courage this time.
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Edited 2 months ago
I'm happy to share that a few of my talk proposals for LPC and OSSummit Japan, which will be held in the second week of December, are accepted.

In OSSummit Japan, I will introduce [1] 'hkml', the mail management tool for Linux kernel development.

In the Refereed track of LPC, I will introduce new DAMON features for page level and fleet wide data access monitoring.

In the "Device and Specific Purpose Memory" micro conference of LPC, I will discuss a plan for utilizing DAMON for access-aware page migrations on general NUMA systems including those for CXL, CPU, GPU and any processors.

In the "Linux System Monitoring and Observability" micro conference of LPC, I will share history and limitations on DAMON's output visualization formats and discuss how we can improve.

[1] https://sched.co/29FmF

#linux #kernel #damon #hkml #ossummit #LinuxPlumbers
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sj

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Reply to @hyeyoo
@hyeyoo @vbabka @ljs Oh, you're right. Maybe I was mistakeenly thinking the patch for removing all the slab allocators[1] is merged ;)

[1] https://lore.kernel.org/linux-mm/20230401094658.11146-1-vbabka@suse.cz/
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sj

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Reply to @ljs@mastodonapp.uk
@ljs @vbabka Let's look forward to the Brno edition of the shirt :)
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sj

sj

Edited 2 months ago
I got my first DAMON t-shirt.

You might need to zoom-in to see why I'm saying it is a DAMON t-shirt, like you may need to zoom in/out DAMON-generated access pattern heatmaps, e.g., 'damo report heatmap --interactive_edit'[1].

[1] https://github.com/damonitor/damo/blob/next/USAGE.md#heatmap-scoping

#linux #kernel #damon #t-shirt
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sj

sj

@KernelRecipes It was an honor to give a talk at kernel recipe, and getting so many grateful questions and discussions about DAMON during and after the talk. The slides are available at https://github.com/damonitor/talks/tree/master/2025/kernel_recipes

#linux #kernel #damon #kr2025

RE: https://fosstodon.org/@KernelRecipes/115253831274830187
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KernelRecipes@fosstodon.org

Kernel Recipes

Edited 2 months ago

@sj on stage about memory: Overcoming Observer Effects in Memory Management with DAMON

https://kernel-recipes.org/en/2025/schedule/overcoming-observer-effects-in-memory-management-with-damon/

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KernelRecipes@fosstodon.org

Kernel Recipes

Edited 2 months ago

@sj DAMON has been upstream in Linux 5.15. Main goal is to have something like a space-time view

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sj

sj

Kangrejos was awesome. I'm now in Paris for presenting [1] DAMON at Kernel Recipes, Tuesday.

[1] https://kernel-recipes.org/en/2025/schedule/overcoming-observer-effects-in-memory-management-with-damon/

#kangrejos #kernelrecipes

RE: https://social.kernel.org/objects/7f1cced2-39e6-4a15-8b0a-ba3cf3b3955b
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sj

Edited 2 months ago
In 2023, I walked [1] on the France route of Camino de Santiago from Burgos to Santiago de Compostela (~500 km) to prepare (walk on days, work on slides and code on nights) for DAMON talk [2] at OSSummit Europe. This year, I walked it again from Saint Jean Pied de Port to Burgos to complete the route, and further from Burgos to Carrion de los condes (~322 km) to prepare for Kangjeros [3] and Kernel Recipes [4]. Now I’m ready to attend talks and made a first draft [5] of my Kernel Recipes talk slides. Switching from a pilgrim to a conference attendee and heading to Kangrejos now. Looking forward to meeting people on Kangrejos and Kernel Recipes!

[1] https://social.kernel.org/notice/AZrKdcNdDyaDwkShou
[2] https://static.sched.com/hosted_files/osseu2023/92/damo_ossummit_eu_2023.pdf
[3] https://kangrejos.com/
[4] https://kernel-recipes.org/en/2025/schedule/overcoming-observer-effects-in-memory-management-with-damon/
[5] https://github.com/damonitor/talks/blob/master/2025/kernel_recipes/damon_kernel_recipes2025.pdf

#kangjeros #kernelrecipes #caminodesantiago
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rostedt

Steven Rostedt

Linux Plumbers 2025 in Tokyo’s Call for Proposals is nearing its end! https://lpc.events/blog/current/index.php/2025/09/08/the-call-for-proposals-is-nearing-its-end/

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josefbacik@hachyderm.io

Josef Bacik

Today is my last day at Meta. This has been the best team I’ve ever been on, and I’ve been on some great teams. Next week I start a new chapter, I will be joining Anthropic to help them scale out their infrastructure and put my decades of kernel and systems experience to use. I will be stepping back from kernel development as my primary job for the first time in my career. I’m sad to leave my colleagues, but I’m excited to try something new and see where it takes me.

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sj

A patch series[1] for making DAMON supports ARM (32bit) with LPAE has just landed on mm-new tree. It was made by a great and joyful collaboration between I and Huawei (Quanmin Yan and Zuo Ze). Hopefully this will land on Linux v6.18.

[1] https://lkml.kernel.org/r/20250822093420.2103803-2-yanquanmin1@huawei.com

#linux #kernel #damon
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vbabka@mastodon.social

Vlastimil Babka 🇨🇿🇪🇺🇺🇦

Looks like the @opensuse Tumbleweed kernel will soon (when 6.17 is final and passes QA) produce a warning when mounting a bcachefs instance... https://bugzilla.opensuse.org/show_bug.cgi?id=1248109

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Edited 3 months ago
DAMON results are arguably hard to understand. And no single visualization fits all. Hence DAMON user-space tool provides a feature[1] that lets users program their own visualization in Python code.

A visualization recently suggested was showing size of memory for different hotness, and sort the size values by the hotness. It can intuitively show cold memory tail. We implemented it as another custom visualization program[2].

The script outputs the visualization in text format, that can easily be plotted as a chart, like attaching.

[1] https://github.com/damonitor/damo/blob/next/USAGE.md#damo-report-access-programming-visualization
[2] https://github.com/damonitor/damo/blob/next/report_access_exec_scripts/idle_time_mem_sz.py

#linux #kernel #damon #damo
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sj

Exploring mails on deep threads with hkml is not that easy. It is easy to miss on what mail currently the cursor is on, and which mail is replying to which mail.

To help this, below three new key bindings are implemented and pushed to master branch of hkml[1].

'w' and 'b' key move the cursor to next and previous words, respectively, similar to those on 'vim'.

'g' key highlights and unhighlights (toggles) the row and the column of the current cursor.

The word-based cursor movement is useful for moving it to beginning of the mail.

The highlighted lines can be useful for seeing on what mail the cursor is on, and what mails are replying to what mails.

[1] https://github.com/sjp38/hackermail

#hkml
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sj

I continued this to allow monitoring accesses that made by only specific group of CPUs. You can do that using damo, like below.

```
$ sudo ./damo start --exp_ops_use_reports y --exp_ops_cpus 0-3,7-8,10
```

Again, note that this depend on gross, buggy, un-upstreamable-as-is hacks.

The initial proposals of these works go back to 2022. So I'm happy to share my first prototype that can at least be tried. So wrote a blog post after a while about this: https://damonitor.github.io/posts/write_only_cpus_only_monitoring/

#linux #kernel #damon #damo

RE: https://social.kernel.org/objects/6090d05e-4257-4b43-99fe-d104cba95054
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Edited 4 months ago
With kernel on the latest damon/next tree[1] and DAMON user-space tool on the latest next tree[2], users can try write-only monitoring via following command.

```
$ sudo ./damo start --exp_ops_use_reports y --exp_ops_write_only y
```

Please note that it is totally experimental, not in an upstreamable shape, and I did nearly no test. It may have many bugs, will be changed a lot, and might not be upstreamed at all. But, you can at least run the experiment.

#linux #kernel #damon #damo #write-only

[1] https://git.kernel.org/pub/scm/linux/kernel/git/sj/linux.git/log/?h=damon/next
[2] https://github.com/damonitor/damo/tree/next
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MM pull request[1] for Linux 6.17-rc1 is merged. There are so many interesting changes. As usual I highly recommend to read Andrew's great summary of the changes. If I pick only two changes that make me happy to see among only DAMON changes,

"mm/damon/vaddr: Allow interleaving in migrate_{hot,cold} actions" from Bijan and Ravi from Micron[*] made DAMON useful for yet another domain that I never expected.

"selftests/damon: add python and drgn based DAMON sysfs functionality tests" increased DAMON test coverage so much thanks to the power of 'drgn', and actually found a real bug[2].


[*] Andrew introduces it as came from me, but the real workers are Bijan and Ravi!

[1] https://lore.kernel.org/all/20250730152806.16f5c618e3af0d3b8dea3159@linux-foundation.org/
[2] https://social.kernel.org/notice/Awb8b5Dbt5hBDsyIdc

#linux #kernel #damon #drgn
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