earlyoom
simdjson
earlyoom | simdjson | |
---|---|---|
60 | 66 | |
2,773 | 18,591 | |
- | 1.0% | |
8.6 | 9.2 | |
21 days ago | 3 days ago | |
C | C++ | |
MIT License | Apache License 2.0 |
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earlyoom
- Earlyoom – Early OOM Daemon for Linux
- Fedora Workstation 39
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earlyoom VS thrash-protect - a user suggested alternative
2 projects | 12 Oct 2023
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Linuxatemyram.com
> The system is not supposed to 'lock up' when you run out of physical RAM. If it does, something is wrong. It might become slower as pages are flushed to disk but it shouldn't be terrible unless you are really constrained and thrashing. If the Kernel still can't allocate memory, you should expect the OOMKiller to start removing processes. It should not just 'lock up'. Something is wrong.
I don't why but locking up is my usual experience for Desktop Linux for many years and distros, and I remember seeing at least one article explaining why. The only real solution is calling the OOMKiller early either with a daemon or SysRq.
> It should not take minutes. Should happen really quickly once thresholds are reached and allocations are attempted. What is probably happening is that the system has not run out of memory just yet but it is very close and is busy thrashing the swap. If this is happening frequently you may need to adjust your settings (vm.overcommit, vm.admin_reserve_kbytes, etc). Or even deploy something like EarlyOOM (https://github.com/rfjakob/earlyoom). Or you might just need more RAM, honestly.
Yeah. Exactly. But as the thread says, why aren't those things set up automatically?
- OOM still a disaster zone
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Fedora spins
It's not that simple: some defaults may differ, and some features may arrive at different times (if ever). For example, earlyoom has been enabled on Workstation since F32, but the KDE Plasma spin got it one release later.
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So what exactly do I do if Linux crashes?
Most answers will answer your question, but you can do better and avoid the freezes in the first place. IME almost every time the system froze up and didn't come back in a few seconds it was out of memory. The obvious solution is to add memory, but you can use Early OOM to kill hungry processes if you're running out of memory instead.
- Why is there no reliable way to receive signal when OOM killer decides to kill you
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What do you do when Linux becomes unresponsive (in a frozen state,mouse clicks or keyboard doesn't work)
It sounds like you're running out of memory though, so if your OS's OOM killer isn't working as well as it should, you can try earlyoom as an alternative.
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Linux Desktop Environments System Usage (Gnome, KDE, XFCE, LXQT, Cinnamon, Mate)
Swap is indeed supposed to prevent this AFAIK. You can though try some tools like EarlyOOM and see if it helps : https://github.com/rfjakob/earlyoom
simdjson
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Tips on adding JSON output to your command line utility. (2021)
It's also supported by simdjson [0] (which has a lot of language bindings [1]):
> Multithreaded processing of gigantic Newline-Delimited JSON (ndjson) and related formats at 3.5 GB/s
[0] https://simdjson.org/
[0] https://github.com/simdjson/simdjson?tab=readme-ov-file#bind...
- 1BRC Merykitty's Magic SWAR: 8 Lines of Code Explained in 3k Words
- Training great LLMs from ground zero in the wilderness as a startup
- simdjson: Parsing Gigabytes of JSON per Second
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Use any web browser as GUI, with Zig in the back end and HTML5 in the front end
String parsing is negligible compared to the speed of the DOM which is glacially slow: https://news.ycombinator.com/item?id=38835920
Come on, people, make an effort to learn how insanely fast computers are, and how insanely inefficient our software is.
String parsing can be done at gigabytes per second: https://github.com/simdjson/simdjson If you think that is the slowest operation in the browser, please find some resources that talk about what is actually happening in the browser?
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Cray-1 performance vs. modern CPUs
Thanks for all the detailed information! That answers a bunch of my questions and the implementation of strlen is nice.
The instruction I was thinking of is pshufb. An example ‘weird’ use can be found for detecting white space in simdjson: https://github.com/simdjson/simdjson/blob/24b44309fb52c3e2c5...
This works as follows:
1. Observe that each ascii whitespace character ends with a different nibble.
2. Make some vector of 16 bytes which has the white space character whose final nibble is the index of the byte, or some other character with a different final nibble from the byte (eg first element is space =0x20, next could be eg 0xff but not 0xf1 as that ends in the same nibble as index)
3. For each block where you want to find white space, compute pcmpeqb(pshufb(whitespace, input), input). The rules of pshufb mean (a) non-ascii (ie bit 7 set) characters go to 0 so will compare false, (b) other characters are replaced with an element of whitespace according to their last nibble so will compare equal only if they are that whitespace character.
I’m not sure how easy it would be to do such tricks with vgather.vv. In particular, the length of the input doesn’t matter (could be longer) but the length of white space must be 16 bytes. I’m not sure how the whole vlen stuff interacts with tricks like this where you (a) require certain fixed lengths and (b) may have different lengths for tables and input vectors. (and indeed there might just be better ways, eg you could imagine an operation with a 256-bit register where you permute some vector of bytes by sign-extending the nth bit of the 256-bit register into the result where the input byte is n).
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Codebases to read
Additionally, if you like low level stuff, check out libfmt (https://github.com/fmtlib/fmt) - not a big project, not difficult to understand. Or something like simdjson (https://github.com/simdjson/simdjson).
- Simdjson: Parsing Gigabytes of JSON per Second
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Building a high performance JSON parser
Everything you said is totally reasonable. I'm a big fan of napkin math and theoretical upper bounds on performance.
simdjson (https://github.com/simdjson/simdjson) claims to fully parse JSON on the order of 3 GB/sec. Which is faster than OP's Go whitespace parsing! These tests are running on different hardware so it's not apples-to-apples.
The phrase "cannot go faster than this" is just begging for a "well ackshully". Which I hate to do. But the fact that there is an existence proof of Problem A running faster in C++ SIMD than OP's Probably B scalar Go is quite interesting and worth calling out imho. But I admit it doesn't change the rest of the post.
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New package : lspce - a simple LSP Client for Emacs
I have same question as /u/JDRiverRun : how do you deal with JSON, do you parse json on Rust side or on Emacs side. I see that you are requiring json.el in your lspce.el, but I haven't looked through entire file carefully. If you parse on Rust side, do you use simdjson (there are at least two Rust bindings to it)? If yes, what are your impressions, experiences compared to more "standard" json library?
What are some alternatives?
oomd - A userspace out-of-memory killer
RapidJSON - A fast JSON parser/generator for C++ with both SAX/DOM style API
nohang - A sophisticated low memory handler for Linux
jsoniter - jsoniter (json-iterator) is fast and flexible JSON parser available in Java and Go
systemd - The systemd System and Service Manager
json - JSON for Modern C++
darling - Darwin/macOS emulation layer for Linux
json-schema-validator - JSON schema validator for JSON for Modern C++
XMousePasteBlock - Userspace tool to disable middle mouse button paste in Xorg
JsonCpp - A C++ library for interacting with JSON.
le9-patch - [PATCH] mm: Protect the working set under memory pressure to prevent thrashing, avoid high latency and prevent livelock in near-OOM conditions
json - A C++11 library for parsing and serializing JSON to and from a DOM container in memory.