Does the cron come into this? Cron tasks can do all sorts of things up to every minute, database changes, file changes, network requests, all contributing to load.
One would expect most core tasks to be fairly well tuned but it maybe there's scope to reduce the frequency of some of these to reduce load (I haven't investigated this).
Then there are plugins which may also have tasks but where perhaps fewer people have looked at the code or examined the performance. I've seen one report of potential for tuning in mod_customcert (#387), this task is run every minute by default. In the absence of any improvement at code/query level this could perhaps be run (for example) every two minutes presumably with a resulting reduction of load with minimal loss of functionality.
Here's another one I've recently run into, file storage wasted by unwanted/unused PDFs (MDL-71909).
If you have the core assignfeedback_editpdf plugin enabled – the default setting – then a PDF is created for every assignment submission even if Annotate PDF isn't selected for that assignment. Worse, if the submission doesn't have a PDF equivalent (such as submitted media files) then a blank PDF is created. Worse still, because the blank PDF is timestamped each one has a different content hash. So you can end up with many unused (and useless!) PDFs in Moodledata which could all be blank.
You can disable this plugin to stop it happening (assuming it's not used for any assignments across the site) – but the submissions still get appended to mdl_assignfeedback_editpdf_queue and not removed (because the plugin is disabled). If you ever subsequently enable the plugin the queue gets processed (by \assignfeedback_editpdf\task\convert_submissions) and you get as many PDFs as there have been assignment submissions (excluding any submissions or mod_assign instances that have been deleted).
So with the no-code-change view I'd recommend disabling this plugin unless this assignment feedback type is actually being used.
Hi Germán
Simply because that group of 40 was accessing the Pi through the wired LAN! In addition there were a handful connected through the wi-fi interface of the Pi configured as an access point, but only via SSH for monitoring purposes.
Maybe you were thinking of the MoodleBox, which has this ~20 user limit, if connected through its built-in access point. That is because of the power limit of the wireless transmitter in the Pi (hardware) and how the network driver of the wireless interface optimized.
If you want to go beyond that limit you need an additional access point. See https://discuss.moodlebox.net/d/60-connect-an-access-point-to-the-moodlebox/7.
Hello Visvanath and all Moodlers! 🌟
This is a fantastic and very important question, especially nowadays with the growing awareness of sustainability and resource optimization! When we talk about creating energy-efficient Moodle servers, we're entering a field that involves both hardware and software, but there's no way to remove significant parts of Moodle without affecting the ability of students to access Moodle pages.
So the solution is to prevent requests from reaching the server. And for that, a CDN is one of the most effective ways to reduce the load on your main server. They work as global distributors of your content, reducing the number of direct requests to the server and improving latency for users in different parts of the world. I have had a very positive experience with BunnyCDN, where I managed to reduce direct requests to the server by up to 90%! Check out this article I wrote on the topic, I think you'll find it quite inspiring: Optimizing Moodle Performance - BunnyCDN. 🌍⚡
In addition to a CDN, implement caching at multiple levels: browser cache, page cache, and application cache (such as Redis or Memcached). This drastically reduces the load on the server by allowing Moodle to load static content directly from the cache without needing to process everything again for each request.
Eduardo Kraus
Professor / Programmer / Passionate about Moodle / Innovation and new products
While CDN's definetly can massively improve performance and user experience if its not your infrastructure serving the content it is someone elses. Caches are definetly a critical part of any Moodle installation at scale and there are some economies of scale to be had here but I'd question them on the energy efficiency front. Any caching requires large volumes of data to be held in memory, large NoSQL databases etc. I'd be really interested to see any specific studies on this.
Hi, Brett! 😄
You raised a very interesting point about the use of cache and CDNs in Moodle, and I’m excited about it!
First, it’s worth highlighting that although caches and CDNs use resources and require memory to store large volumes of data, the performance and energy efficiency gains they bring can be significant, especially in large-scale installations like Moodle. What many don’t realize is that the resource consumption of cache is actually much lower compared to the processing Moodle needs to handle when responding to all requests directly.
Imagine that without cache, each simple request to load an image (for example, via pluginfile.php or theme/image.php) has to go through several steps: opening multiple tables in the database, authenticating the user, checking permissions, and only then delivering the file. This not only increases latency but also adds a significant load on the database and the application server.
With cache in place, on the other hand, these static files (like images, PDFs, videos, etc.) are served directly from the cache, eliminating the need to query the database. This drastically reduces backend processing, frees up server resources for more critical tasks, and lowers energy consumption.
The use of CDNs and local cache reduces energy usage because the main server doesn't need to handle so many repetitive requests. This also results in a better experience for the end-user, with faster load times and less strain on the server.
Eduardo Kraus
Professor / Programmer / Passionate about Moodle / Innovation and new products
HP EliteDesk 800 G1 DM and RPi 4B are worlds apart in server performance. I get consistently a score of only 220 with a RPi 4B 4G: https://moodle.org/mod/forum/discuss.php?d=464548#p1864999. Compare that to the score of 40 with the hp. (lower the better, in a logarithmic scale, so 40 is more than 5.5 times better than 220).
Discovered that the original YouTube nerd had made an "unboxing" video an year ago:
Renewed i5 Mini PC: HP EliteDesk 800 G2
https://www.youtube.com/ watch?v=ZPX3A7YS-6Q (remove the blank)
Suspiciously good to be true:
Tiny Linux kernel tweak could cut datacenter power use by 30%, boffins say
Not bad for 30 lines of code
