Blinking Cursor Devours CPU Cycles in Visual Studio Code Editor (theregister.co.uk)

An anonymous reader shares a report on The Register: Microsoft describes Visual Studio Code as a source code editor that's "optimized for building and debugging modern web and cloud applications." In fact, VSC turns out to be rather inefficient when it comes to CPU resources. Developer Jo Liss has found that the software, when in focus and idle, uses 13 percent of CPU capacity just to render its blinking cursor. Liss explains that the issue can be reproduced by closing all VSC windows, opening a new window, opening a new tab with an empty untitled file, then checking CPU activity. For other macOS applications that present a blinking cursor, like Chrome or TextEdit, Liss said, the CPU usage isn't nearly as excessive. The issue is a consequence of rendering the cursor every 16.67ms (60 fps) rather than every 500ms.

Comments

Holy Blinking Cursor, Batman!

[BeerCat]

13 per cent CPU. For a blinking cursor. That's... impressive.

But not in a good way

Re:Holy Blinking Cursor, Batman!

[drnb]

13 per cent CPU. For a blinking cursor. That's... impressive. But not in a good way

This is why coding tests are given during job interviews.

Re:Holy Blinking Cursor, Batman!

[number6x]

Reminds me of the map of system calls in Apache vs MS IIS. An exercise in design analysis.

Re:Holy Blinking Cursor, Batman!

[lgw]

Yeah, my old Commodore 64 had a blinking cursor, and it somehow managed that remarkable feat with an 8-bit 6510 CPU running at 1MHz!!!

Behold the power of Javascript! It gives a modern PC with 8-16 GHz of total CPU ... less actualy processing power than a Commodore 64.

Well done JS engine guys. Well done.

Re:Holy Blinking Cursor, Batman!

[Anonymous Coward]

I hire C++ developers. I give a simple coding test to all applicants. 95% of all coders fail even the simplest of tests. There's a reason that trivial tests like FizzBuzz are used during programmer interviews. That's because most "programmers" are utter crap. They don't know their tools. They don't know the language that the program in. They don't stay up-to-date. They cannot reason about problems. 95% can't do the simplest of problems. You have to really deep before you find people who can talk about design principles, design by contract, etc.

"Tell me what a class invariant is."

Blank stare.

"What is the Liskov substitution principle?"

Deer in headlights.

Thank you for your time.

I work in the financial industry. We pay shit-tons of money if you know how to engineer software. But even here the talent pool is miserable.

Re: Holy Blinking Cursor, Batman!

[Anonymous Coward]

There's a difference between remembering the piece of trivia that is the name a certain environment calls a concept and understanding the concept.

The question becomes: are you looking for a software engineer, a computer programmer, or a trivia expert?

Re:Holy Blinking Cursor, Batman!

[lgw]

The engine devs are not the language authors. I think the language authors are idiots, too, but not for any reason related to this story.

Re:Holy Blinking Cursor, Batman!

[CanadianMacFan]

"What is the Liskov substitution principle?"

I didn't know what it was until I looked it up in the article. So basically you want me to remember that some guy came up with a name for using inheritance and if I don't remember it I'm a bad programmer?

Test to see how the person will fit into your team because no matter how great they are if they disrupt how the team works. Then for programming skill and then for things like remembering the exact definition of terms that they could use Google to get.

Re:Holy Blinking Cursor, Batman!

[TechyImmigrant]

It gets worse. He only hires C++ developers who are MIT alumni and who know Barbara Liskov personally.

You had me at C++.

Re:Holy Blinking Cursor, Batman!

[TechyImmigrant]

Some tests make sense. Others are head-scratching. For UNIX admin jobs, I have been asked moving a database from first normal form to DK normal form, but in reality, I've yet to see any DBA go past 3NF unless it is some specialized data warehouse/data mart task.

It was 1st NF --> 2nd NF --> 3rd NF --> BC NF when I went to college. I'd never get past your interview. But then I don't want a DB job so it's all good.

Re: Holy Blinking Cursor, Batman!

[Darinbob]

I agree there. I have used many programming languages and so many of them make up their own terms for things that were previously well known by different names in the industry. Most of these new terms were for things that were known in the 70s and 80s. I think a lot of people who are in their own bubble, making up their own terms, without knowing what goes on elsewhere.

Re:Holy Blinking Cursor, Batman!

[Anonymous Coward]

13 per cent CPU. For a blinking cursor. That's... impressive.

The failure to understand anything more than any one level of the stack is the root cause of the problem:

In fact, I'm willing to bet it's not a coincidence that it's 13%. It's likely 12.5%, as in 100% of one thread on a quad-core CPU with hyperthreading enabled, then rounded up to 13% for the presentation in the task manager. On a dual-core with HT, it'd be 25%, on a dual-core without HT, it'd be 50%, and if anyone can get it to run on an old single-core Pentium IV or something it'll just peg that CPU.

People would have to know something about hardware to figure that out, and webdevs, well, they just... don't.

Re:Holy Blinking Cursor, Batman!

[sexconker]

That's because most "programmers" are utter crap. They don't know their tools. They don't know the language that the program in. They don't stay up-to-date.

I don't "know the tools" or "know the language" until I'm fucking using them. Then I google whatever the fuck it is I need to do using whatever the fuck it is some clown has put in front of me, RTFM, and get it done. Interviews test for the dumbest fucking shit. I for one generally don't care what fucking language or environment I'm in. With documentation (the fucking internet 99.9% of the time) learning how to do X in Y is trivial. Knowing that you need to do X instead of x is the trick. When you give an applicant a test to do X in Y, you're just testing if they know Y and maybe if they have memorized X. You're not finding out if they understand anything or can think critically.

They cannot reason about problems. 95% can't do the simplest of problems. You have to really deep before you find people who can talk about design principles, design by contract, etc.

When your "problems" are all pulled from the same "Shitty Questions and Tests for Shitty Interviews" site/book, what do you expect? If you're looking for people who talk about "design principles" or "design by contract", you're retarded. There are only three design principles: Correct, secure, and fast. There is only one design contract: Deliver X for $Y. If you don't understand what X is or why it's X and not x (even if the customer doesn't, or if the customer asks for X when they need x) then you're gonna have a bad time. See Oracle and IBM and anyone who's ever contracted with them.

You're getting mindless applicants because you're asking mindless questions. You cannot discern a competent programmer/developer from an incompetent one because you're looking for memorization, certifications, etc. Of course, the people conducting the interviews are typically not competent programmers/developers, so they don't know what else to look for or how else to evaluate applicants.

Re:Holy Blinking Cursor, Batman!

[Anaerin]

Opening VIM is the easy part. If you can successfully CLOSE VIM afterwards, that's the passing point.

Re:Holy Blinking Cursor, Batman!

[thegarbz]

But even here the talent pool is miserable.

The talent pool is quite large but you're not looking for talented engineers. You're looking for people with a photographic memory.

Re:Holy Blinking Cursor, Batman!

[mattsday]

Preferences and then:

"editor.cursorBlinking": "solid",

Job done!

Re:Holy Blinking Cursor, Batman!

[avandesande]

Obviously the OP suffers from incredibly lazy thinking to believe that he can find a good candidate with just a couple of questions. You certainly don't want to work there.

Re:Holy Blinking Cursor, Batman!

[bored]

You probably just made it consume 100% of the CPU as it tries to flash the cursor at an infinite rate...

Re: Holy Blinking Cursor, Batman!

[drnb]

A perfectly fine answer is "No, I've never heard of it before. What is it?" Then we can have a conversation.

Perfect. Sadly, then you write the following ...

I'm not looking for trivia experts ... A lot of my questions are to probe whether they have bothered to read books that are not typically part of the college curriculum but are important references for a professional software engineer.

Perhaps a beginning software engineer. As one with 30+ years of experience I might look at a summary of Martin's SOLID topic and think "not much new here", low priority or pass.
"S Single responsibility principle
a class should have only a single responsibility (i.e. only one potential change in the software's specification should be able to affect the specification of the class)
O Open/closed principle
“software entities should be open for extension, but closed for modification.”
L Liskov substitution principle
“objects in a program should be replaceable with instances of their subtypes without altering the correctness of that program.” See also design by contract.
I Interface segregation principle
“many client-specific interfaces are better than one general-purpose interface.”
D Dependency inversion principle
one should “depend upon abstractions, [not] concretions.”"
https://en.wikipedia.org/wiki/...

I find it interesting that so many latched on the Liskov question -- and read their own deficiencies into the question -- and ignored the one about invariants

Well the Liskov question was much more trivia than invariants. Liskov mere formalized in an academic sense what many skilled programmers already knew, so many reading Liskov's abstract would probably take a pass. Do not confuse the concept with the name of someone who wrote about the concept.

What may seem new and innovative to the trade to a person with modest experience may not seem new to someone with extensive experience. Agile for instance, a bit of it seemed merely common sense to those of us with a bit of experience.

These are concepts. We have a language that we use to discuss software engineering concepts.

Correct on the first, wrong on the second with respect to Liskov, you have a niche buzzword. Many SOLID adherent may not recall the name that L represents but still recall the concept.

Focus on a buzzword recognition and you may miss someone who actually understands the concept very well. Again, I refer back to your first sentences which were absolutely spot on correct: "A perfectly fine answer is "No, I've never heard of it before. What is it?" Then we can have a conversation."

Re:Holy Blinking Cursor, Batman!

[arglebargle_xiv]

"Tell me what a class invariant is."
Blank stare.
"What is the Liskov substitution principle?"
Deer in headlights.

Prove that every even number > 2 can be expressed as the sum of 2 primes

Empty look.

Show that the Riemann zeta function has its zeros only at the negative even integers and complex numbers with real part 1/2.

Panicked expression.

Demonstrate that If k graphs each having k vertices have the property that every pair of complete graphs has at most one shared vertex then the union of the graphs can be colored with k colours.

Runs from room.

Sigh, kids these days...

Re:Holy Blinking Cursor, Batman!

[drnb]

Opening VIM is the easy part. If you can successfully CLOSE VIM afterwards, that's the passing point.

Extra credit for a minimal number of beeps while using it. :-)

Re: Holy Blinking Cursor, Batman!

[Anonymous Coward]

This reminds me so much of that rookie question: "what programming languages do you know?"

I dunno, with a reference manual, all of them. It is immaterial because I'm going to have to learn another one for the next project or the next software platform.

And they'll have their own names for common ideas, which you'll see once and realize what it actually is.

Re:Holy Blinking Cursor, Batman!

[Bengie]

Knowledge seems inversely related to understanding. /sarc

But really. In psychology, it is known that accessing memory while attempting to learn hampers your ability to learn. Internalizing a concept such that you no longer need to access memory, but instead "just think that way" frees up your memory. A typical person can only hold a hand full of concepts in their head at once. If you're dealing with a complex system, memorizing it is incredibly inefficient. Learning to think like the system allows you to effectively hold it all in your head without having to use your memory.

Like Minecraft, if you instead algorithmically generate your "memories" you can free up your actual memory. Minecraft manages to compress an entire map down to a small seed and only has to store the differences. This is how you deal with large complex system.

I literally have a memory disability, but I can manage hugely complex systems in my head by designing the system using simple patterns and making sure the patterns can express the complexity of the system. Like a fractal. I compensate for my disability by "regenerating" my memory in real time. I have difficulty telling the difference between something I just thought of or something that I remembered because thinking is nearly the same as remembering for me.

This breaks down outside of logical systems. Day-to-day activities give me issues. Sometimes I forget my own birthday. It took me nearly 6 months to remember my wife's name while we were dating, and I saw her almost every day. I had to give her a pet name. At first she didn't like it, but it grew on her. Most people who meet me think I'm fairly normal but slightly dunce. That is until they get me working on something that requires abstract reasoning.

I think anyone could do what I do, but I take a much longer time getting up to speed because it takes time for me to internalize a concept into my way of thinking. But once I integrate a concept, I no longer have to remember anything about it, it become natural for me to think that way. I am forced to do this because of my disability, but if people were not in such a hurry to crank out some code, they to could free up their limited memory for other more important things, like learning.

Re: Holy Blinking Cursor, Batman!

[apparently]

God, I bet the nickname your subordinates have for you is fucking priceless.

That's what you get...

[Kormoran]

...when you hand the task over to the HALO crew. Absolutely NO flicker, man. Oh, wait...

Maybe they shouldn't use Javascript ...

[drnb]

13% of CPU at 60 fps. Maybe they shouldn't use Javascript and a cross platform framework for drawing the cursor. ;-)

Probably a minor oversight. Will likely be fixed.

[Anonymous Coward]

Seems like a minor oversight. It will probably be fixed soon, if it hasn't already been.

Microsoft has actually done a good job with Visual Studio Code. It's a lot better to use than, say, Atom or EMACS. It has some great plugins, they're easy to install, and overall it provides a good compromise between a plain text editor and a full-featured IDE.

I'm not going to hold this minor bug against them.

blinking and beeping and flashing -

[fustakrakich]

they're *flashing* and they're *beeping*. I can't stand it anymore!

Devil in the Details...

[EndlessNameless]

Is it rendering the cursor specifically at 60 FPS, or is it the entire active window?

Because I can imagine a good reason for rendering the active window in an IDE every frame. Your brain is definitely capable of registering visual changes faster than once every 500ms.

If you have smart syntax highlighting, you want the squiggly lines, tab-complete indicators, color coding, and highlights to appear ASAP. The sooner you notice a mistyped function name, the less characters you have to back over to fix it.

A fast, responsive window refresh is essential to modern IDEs.

I mean, feel free to call them out if Eclipse or whatever is much better at it, but I can totally see why they would rerender the entire window. If it is the active window (per the summary), then you can assume it's being used and therefore deserves the most responsive output possible.

Re:Devil in the Details...

[drnb]

Is it rendering the cursor specifically at 60 FPS, or is it the entire active window? Because I can imagine a good reason for rendering the active window in an IDE every frame.

Pro tip: when rendering an entire window, or an entire screen in a game, you might want to consider "dirty rectangles" and only redraw what has changed.

Re:I think there is more to it.

[RatherBeAnonymous]

According to TFA, adding "editor.cursorBlinking": "solid" to the app's settings.json fixes the high CPU consumption. That makes me think there isn't anything more to it.

Re:Probably a minor oversight. Will likely be fixe

[Richard_at_work]

It looks like its actually an underlying issue with Chromium, which is what powers Electron, the UI framework which VS Code is based on.

https://bugs.chromium.org/p/ch...

Simple CSS Keyframe Animation Causes Too High CPU Usage

Steps to reproduce the problem:
It happens on my Mac.

Demo page here: http://output.jsbin.com/vogaxa

Add a simplest keyframe animation to an element and Chrome will use 5-6x more CPU than it should.

e.g: .blinking { animation: 1s blink step-end infinite; }

@keyframes "blink" {
    from, to { visibility:hidden; }
    50% { visibility:visible; } }

What is the expected behavior?
CSS animation should consume equal (or close to equal) CPU load than its Javascript animation alternative.

Javascript setInterval consumes around 1.2% CPU on my Mac (Chrome's task manager)

1.2% for Javascript animation of a blinking cursor btw is the same usage that I get with no animation and the default cursor inside an input element.

CSS animation should produce the same results.

What went wrong?
CSS keyframe based animation consumes 7-8% CPU which is unjustified for such a simple case.

60 FPS is the minimum these days

[tobiasly]

Well I would hope that a modern IDE released in 2017 would have 60 FPS! I also have the 4K cursor, HDR cursor, 3D cursor, Retina cursor, and VR cursor plugins all enabled, but I realize that may be overkill for some people. As soon as I get my new water cooling rig set up it'll be buttery smooooth.

Re:Is it a good test?

[mark-t]

Using the CPU draws more power than if it were just idle, so it is incorrect to say it does not matter.

Re:Probably a minor oversight. Will likely be fixe

[Tailhook]

Microsoft has actually done a good job with Visual Studio Code.

If you're willing to completely dismiss performance concerns then yes, great work. On the other hand, if you care about performance, and memory usage, it's pretty hard to do worse than VSCode without including including something like Eclipse or Intellij in the survey.

Re:Probably a minor oversight. Will likely be fixe

[Grishnakh]

No, it sounds like the problem is the insane idea of running local code through a web browser. The web itself is probably the most Rube Goldberg-esque way of displaying interactive data and controls to a user (HTML, a backend language like PHP/Java, a client-based language (JavaScript), and then a crappy markup language for style attributes (CSS)). It's understandable how it evolved, but it makes no sense at all to use this for local applications.

This is a bit absurd...

[ZorinLynx]

How is it that four decades into the personal computing era and ANYTHING in the UI is using any significant amount of CPU?

A blinking cursor?? The Apple II had a blinking cursor in 1977, and it was implemented in hardware. It used zero percent of the CPU.

My gods, programmers have gotten lazy. What's next, extra CPU consumption for bold text? The system slowing down every time it beeps?

don't use the 'web stack' for desktop applications

[epyT-R]

It duplicates functionality and kills performance

Not a Microsoft Issue

[nuckfuts]

Funny how the summary and the article both start by saying...

Microsoft describes Visual Studio Code as a source code editor that's "optimized for building and debugging modern web and cloud applications.

But then the article goes on to say...

The underlying issue is with Chromium, which is a part of the Electron Shell (Visual Studio Code and others like Atom and Slack utilize this shell in their apps)"

and then...

Google Chrome product manager Paul Irish, posting to a thread on Hacker News, said, "Chrome is doing the full rendering lifecycle (style, paint, layers) every 16ms when it should be only doing that work at a 500ms interval. I'm confident that the engineers working on Chrome's style components can sort this out, but it'll take a little bit of work."

Re:Probably a minor oversight. Will likely be fixe

[DickBreath]

Please do not knock Emacs.

Emacs is very popular. Popularity seems to correlate highly with the set of users who once started up Emacs, were unable to figure out how to exit from Emacs, then had no choice but to write Emacs Lisp extensions to accomplish all other necessary tasks.

I don't think VS Code can make that claim.

Yet VSC is better than Eclipse, NetBeans, etc

[Anonymous Coward]

I've been a web developer for many years. I don't particularly like the entire web stack. Yes, it's shitty in many ways.

But here's the thing: somehow, Microsoft has managed to make an advanced text editor that's responsive, extensible, and enjoyable to use on all of the major platforms. And they've done it using some of those web technologies.

Visual Studio Code is an absolute pleasure to work with compared to IDEs like Eclipse or NetBeans or Intellij. It feels much faster than them, even with this blinking cursor issue (which as a long time Visual Studio Code user I didn't even notice). It's easier to extend. The plugins that others have written are much better. It's a smaller initial download. It's easier to keep updated.

Then there's a native text editor like Gedit. One look at Gedit's UI makes me want to vomit.

Kate is perhaps the only native text editor that isn't a complete joke. But it's too tied to KDE to make it easily usable on non-Linux platforms.

I'd love to use a native or pseudo-native (like Java-based) text editor that offered the benefits of Visual Studio Code. But I've yet to find one that comes anywhere close to comparing to Visual Studio Code.

Rag on the technologies used to build Visual Studio Code all you want. All that I know is that it's a piece of software that works much better than all of its competitors.

Re:Maybe I'm just out-of-touch...

[epyT-R]

The constant unyielding unending march of useless abstraction.

hardware (hypervisor) -> kernel (per process hardware abstraction for userland) -> interpreted runtimes (nodejs/java/.net etc).

That last part is why modern 'apps' are bloated piles of garbage that need multighz machines to be responsive doing things that could be done on a 486 (eg winNT/mirc on a 486 vs discord on a haswell@4.7ghz). The argument is security and ease of development (zomg! cloud!). The former's been readily disproved and the latter sacrifices significant capability and performance. I think we're well past the point of diminishing returns and into the realm of significant drawbacks.

Gloves off!

[Kludge]

OK, buddy, vi vs. emacs flame wars were funny, and perhaps justifiable.
But comparing VS to emacs?? No freaking way! Emacs totally kicks VS ass.
And it never used 13% of my cpu to flash a cursor.

Terrible interview questions ...

[drnb]

What is the Liskov substitution principle?

That is a very poor question. It exhibits the common naive programming test that is more of a trivia test, or basically a programming test derived from some old college quiz. Better questions ask people to perform relevant tasks or to discuss relevant problems. For example rather than ask about "Liskov", ask about the concepts involved:

Q. A Square class is derived from a Rectangle class. Function foo has a non-const parameter of type Rectangle. Function foo is called with using a variable of type Square. Is this safe, if not why?

Note that in the discussion they may inadvertently discuss class invariants.

You say that some programmers do not understand or lack certain tools. The same is true for managers, and your hypothetical questions suggest that you may be lacking the tools necessary to conduct technical interviews and evaluations.

Re:don't use the 'web stack' for desktop applicati

[djbckr]

I partially agree. But I have a situation where I need to make a moderately simple app that reads/writes local files and calls out to utility command-line tools, and I need it to be cross-platform.

I've researched high and low for a system that doesn't require me to learn a friggin huge framework (QT?), in a language I don't care to use (C/C++)** or an unreliable end-user setup (Python UI or Java Swing)

I just need simple and I need it to work. Yes, Electron is bloated, but it's simple (to build apps with), it works on all platforms, and it allows me to build an app in a few days rather than a few weeks. And the performance for what I'm doing is perfectly acceptable.

** I don't dislike those languages, they are just overkill to get something simple done