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

sj

Edited 2 days 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

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

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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sj

sj

Edited 10 days 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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sj

sj

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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osandov

Omar Sandoval

@sj recently started using drgn to add more DAMON selftests, which is a super interesting use case that I didn't envision: https://lore.kernel.org/all/20250628160428.53115-1-sj@kernel.org/. It has already found a real bug! https://lore.kernel.org/all/20250719181932.72944-1-sj@kernel.org/
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vbabka@mastodon.social

Vlastimil Babka 🇨🇿🇪🇺🇺🇦

BTW, this year we have quite an early "save the date" landing page for LSF/MM/BPF 2026 https://events.linuxfoundation.org/lsfmmbpf/

And AFAIK the first time it's going to be happening outside of North America!

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sj

With great stress comes great stress reliever.
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linuxplumbersconf@mastodon.social

Linux Plumbers Conference

All microconferences (MCs) at LPC 2025 have been accepted! It is time to submit topics to your favorite MCs.

Please check out our latest blog post for the list of MCs, and how to create a ideal MC topic.

https://lpc.events/blog/current/index.php/2025/07/25/all-microconferences-have-been-accepted/

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phoronix@masto.ai

Phoronix

Intel Announces It's Shutting Down Clear Linux

The most depressing news of the week: Intel is ending their performance-optimized Clear Linux distribution. Over the past decade the Clear Linux operating system has shown what's possible with out-of-the-box performance on x86_64 hardware... Not just for Intel platforms but even showing extremely great performance results on AMD x86_64 too. But with the cost-cutting going on at Intel, Clear Linu…
https://www.phoronix.com/news/Intel-Ends-Clear-Linux

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linkersec@infosec.exchange

Linux Kernel Security

Bypass Kernel Barriers: Fuzzing Linux Kernel in Userspace With LKL

Xuan Xing & Eugene Rodionov gave a talk about fuzzing the Linux kernel interfaces fully in user space using LKL (Linux Kernel Library).

Video: https://www.youtube.com/watch?v=Wxmi-2ROYNk
Slides: https://static.sched.com/hosted_files/lssna2025/01/Bypass%20Kernel%20Barriers_%20Fuzzing%20Linux%20Kernel%20in%20Userspace%20with%20LKL.pdf

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sj

Bijan's DAMON patch series[1] for dynamic NUMA memory weighted interleaving that shows ~25% performance improvements on a test is now merged into mm-new, and looks good to me. I'm more than exciting to see this is on the track and grateful to have a chance to participate!

[1] https://lore.kernel.org/20250709005952.17776-1-bijan311@gmail.com

#linux #kernel #damon #interleaving
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sj

sj

And OSSummit NA 2025 DAMON talk video is now available: https://youtu.be/Ou4BQQ0Ved8?si=ZrhjCGI4gRyJmODn

#linux #kernel #damon #ossummit #ossummitna #ossummitna25

RE: https://social.kernel.org/objects/f03afaa9-5786-49eb-8c1d-2b6b6261685e
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sj

sj

Access pattern heatmap is powerful visualization, but exploring the time/space is not that easy[1]. To help that, we added an interactive zoom and scroll mode of the heatmap. You can try that with `damo report heatmap --interacrive_edit`. Attaching a demo gif.

[1] https://damonitor.github.io/posts/why_the_heatmap_is_not_showing_the_expected_access_patterns/

#linux #kernel #dmon #damo
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sj

Edited 1 month ago
OSSummit NA was great. I met old and new great people. DAMON talk was also done very well, thanks to great audiences. The video would be available soon. Meanwhile, you could get the slides for the talk at the conference web site[1] and GitHub[2].

[1] https://sched.co/1zfmE
[2] https://github.com/damonitor/talks/tree/master/2025/ossna

#linux #kernel #damon #ossna
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lwn@fedi.lwn.net

LWN.net

Bcachefs may be headed out of the kernel

https://lwn.net/Articles/1027289/

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kees@hachyderm.io

Kees Cook

Edited 1 month ago

This graph is the one I'm most excited about: the lifetime of security flaws in Linux is finally starting to get shorter (and the number of fixed flaws continues to rise).

https://hachyderm.io/@LinuxSecSummit@social.kernel.org/114750428620118674

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lwn@fedi.lwn.net

LWN.net

LSFMM+BPF 2025 reporting complete

https://lwn.net/Articles/1026338/

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corbet

Jonathan Corbet

It took a long time and over 60 articles but, at @lwn, we have finally managed to complete our reporting from the 2025 Linux Storage, Filesystem, Memory Management, and BPF Summit. If you want to know what is going on in those core parts of the kernel, this is the place to look.

We've put together an EPUB version of the whole set as well — good bedtime reading!

https://lwn.net/Articles/1026338/
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sj

An interesting ISCA'25 paper for better memory tiering is published. The paper uses DAMON and masim for showing access patterns of artificial and realistic workloads.

https://dl.acm.org/doi/10.1145/3695053.3731001

#linux #kernel #damon #masim #memory_tiering
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