At any give time, there are 8 in the run queue: I have 8 cores on my machine but there are 16 CPU-intensive processes running, all vying for CPU time. With those processes booted, I ran :observer.start. System.schedulers_online is a helper function that returns how many cores are available to the BEAM: for _n A.gen_recursive() end) Then I ran the following loop to spawn twice as many processes as I have cores. # define a module function, which can call itself recursively On my computer, I popped open iex and defined this recursive function which performs a CPU-intensive task: defmodule A do In our previous example of a single-core machine with a single scheduler juggling 10 CPU-intensive processes, the run queue would be pegged at 9: there are 9 processes that want CPU time, but are awaiting their turn because there aren't any idle cores. When a process needs CPU time but can't be scheduled immediately, it enters its scheduler's run queue.Īn item is in the run queue because you have more work than you have CPUs to do it. Of most interest to us was the "Run Queue" stat. This tab shows you memory usage, helpfully broken out between things like processes and binaries (strings). The "System" tab is the first one you see after launching Observer: A process waiting on an I/O operation – say, a request to a remote webserver – uses almost no resources (outside its memory allocation) while it waits for a response. Utilizing all cores efficiently is half the motivation for using processes. Naturally, if you run those same 10 processes on a multi-core machine, the work will be distributed among those cores evenly. If you have ten processes running CPU-intensive tasks on a single-core machine, the scheduler will distribute CPU core time between them: it will allow Process A to run for a bit, then interrupt it to give Process B a little time, and so on. A scheduler distributes "air time" on a CPU core among processes. The BEAM boots a scheduler for each core on its host machine. Processes are managed by the BEAM, not the underlying operating system. Erlang processes are lightweight and fast to create and terminate – they can send messages to one another, but each has its own isolated memory. Processes and schedulersĮrlang was built from the ground up to support tremendous concurrency. We'll start with the fundamentals of the BEAM: processes and schedulers. So I'll switch between describing properties of the Erlang VM (the BEAM) and how Observer helps you inspect them. To understand the insights Observer is presenting, you'll need to know a little about the Elixir/Erlang runtime. Observer has a lot of functionality, but this post will focus on the parts we found most helpful in our investigation. You can see the overall health stats of a running node, understand how cores are being utilized by the scheduler, and drill down to individual processes to see if anything is amiss: It's like Activity Monitor or htop for the BEAM. Observer is a great diagnostic tool for Elixir/Erlang applications. Nonetheless, our performance benchmarks degraded – the machine felt overloaded. All cores on our machine were evenly utilized, consistently at about 40%. We recently experienced some puzzling runtime characteristics: our machine reported a high load average but only moderate CPU utilization. We're hiring, no Elixir experience required. We use a suite of OTP tools to sync data in real-time. Improved and new localisations ( 36 languages in total).Want to work on challenging distributed systems problems with Elixir and OTP? Sequin lets developers integrate with APIs using Postgres. Reorderable dropdown menus, with the ability to hide sections. Additional options, like dual line menu bar clocks, and condensed text for showing more in less space. Hotkeys to open and close menu dropdowns, for quick keyboard access. More colors and theme options, including light and dark vibrant menu dropdown backgrounds. Notifications, based on CPU, network, disk, battery, weather and other events. Refined menu bar items, dropdowns and other aspects match the new design of macOS 11 Big Sur. Weather with current temperature, hourly forecast, weekly overview and so much more.
0 Comments
Leave a Reply. |