3 ms·

I disagree about JIT performance not mattering. I enabled "Lockdown Mode" on iOS which disables the JIT for the mentioned security reasons, and it causes a very

by varenc 29d ago

I disagree about JIT performance not mattering. I enabled "Lockdown Mode" on iOS which disables the JIT for the mentioned security reasons, and it causes a very noticeable lagginess on many sites. Of course, the primary cause is the unnecessary JS monstrosities wasting CPU cycles. But practically speaking I can say that disabling the JIT results in a very subpar experience of many JS heavy pages.

Rohansi 29d ago
It will also increase power consumption because your CPU has to do more work to run the same code.
timr 29d ago
That's largely because a lot of developers have made the devil's bargain of replacing standard web stuff with badly re-implemented JS versions of same. People did it because they could, but never considered if they should. See most of the ecosystem around React, for reference. It's idiotic that things like URL management are done in Javascript. Or form controls. I guarantee that if we stopped doing this kind of stuff, JIT wouldn't matter. To some extent this is just saying "developers will depend upon the performance given to them", and that's true, but it's also true that as soon as things like V8 and Node appeared, JS became ubiquitous. Pandora's container, if you will.
- vickychijwani 29d ago
  That's largely because a lot of developers have made the devil's bargain of replacing standard hardware and OS primitives with badly re-implemented C versions of same. People did it because they could, but never considered if they should. See most of the ecosystem around modern systems software, for reference. It's idiotic that things like memory layout and bit-level hardware management are done in C abstractions. I guarantee that if we stopped doing this kind of stuff, compiler optimizations wouldn't matter. To some extent this is just saying "developers will depend upon the performance given to them", and that's true, but it's also true that as soon as things like compilers and standard libraries appeared, C became ubiquitous. Pandora's container, if you will.
  - timr 29d ago
    > It's idiotic that things like memory layout and bit-level hardware management are done in C abstractions. I guarantee that if we stopped doing this kind of stuff, compiler optimizations wouldn't matter. Cute, but no, not even close to a good metaphor. The C example is abstracting away fundamental complexity in a new platform. The other is completely re-writing -- in duplicate and slightly broken -- what the platform gives you for free. There's nothing about implementing form controls or URL management in JS that is more abstract. It's just different; a downstream bad decision that branches off a long tree of other bad decisions. The equivalent level of idiocy in a C-related metaphor would be...I dunno...if you decided that you didn't like the way that header files worked, and decided to keep the C compiler, but build an external header-file management system in Fortran [1] that calls the C compiler for you. Or even closer to the JS metaphor, you shipped a special C compiler that had an embedded interpreted language that only activated at compile time, and you then used that language to allow any user to fundamentally change the syntax of C. (It hopefully shouldn't be lost on you that this exact approach to language features has been repeatedly tried in the javascript world, including right now, with package management. But see also: typescript, coffeescript before that, Dart, etc. Javascript is a mess, and history repeats itself with regularity about every 5 years.) [1] ...and then you re-write that about sixty times, each time being slightly incompatible with the last, and all having different fundamental incompatibilities with C headers.
- grishka 29d ago
  > See most of the ecosystem around React, for reference. I've never used React myself, but what I've heard about it makes me question my own sanity. So are you going to tell me that instead of just updating the DOM tree directly I'm going to apply the changes to my data, then pass the entire model to the framework, which would then diff it with the previous version to get the changes back out, it would then call my functions that return components, and it would then diff the virtual DOM to find out what changed, and only then would it update the actual page? Why the fuck would anyone ever want that? What's so hard about simply changing the innerText or inserting elements or whatever? Oh and now Google and Apple are insisting that this is the way to do UIs in native apps as well, with Compose and SwiftUI respectively. The way the front end developer community seems to largely encourage learning top-down isn't helping either. I'll forever remember that one guy we made a small project with. He learned React but had no clue what "send a request" and "pass a parameter" means, and I had to explain him how to use XHR.
  - leptons 29d ago
    The DOM is the slowest part of the browser. It's not Javascript, it's the DOM. React is an attempt to manage the slowness of the DOM. One seemingly small change to a page (like setting innerText) can have many ripple effects with reflow on mamy parts of a page. With thousands of DOM elements on a page, the DOM becomes a bottleneck. This isn't the fault of front-end developers, and it's not really the fault of browser developers. HTML/CSS/JS is a very powerful system, but it's also complex and can cost a lot of compute. When you understand this, then the reasons for React and other front-end frameworks become easier to accept.
    - exe34 29d ago
      You may not need react. If you want to make the smallest possible change to the dom to reduce latency, then make the smallest possible change to the dom. Choose solidjs. (Not a sponsored post).
    - grishka 29d ago
      > One seemingly small change to a page (like setting innerText) can have many ripple effects with reflow on mamy parts of a page. I haven't looked into how browsers actually do it, but my mental model for it is that if something changes, this merely sets a flag on that element or its parent that its layout is not valid any more. Then, on next vsync, all the elements that have this flag set have their layout recalculated, potentially going up the tree as necessary. The only exception is if your script tries to get any layout-related property, e.g. offsetWidth. Then, as if as part of the getter of such a property, the layout recalculation will run immediately. That is to say, if you need to make a lot of changes to the DOM, you should make them within one JS invocation so only one layout pass happens sometime after you're done.
- tgv 29d ago
  The problem is not url management. That should happen just once or twice during the life cycle of a page. If it takes 0.1ms or 1ms doesn't have any impact on the usability. One of my problems was that I wanted to show data in the browser. It is a convenient delivery platform, after all. However, Chrome (and Chrome in particular) has tremendous trouble displaying large pages. A 400x400 table takes a long time to render. I could solve that in JavaScript. I had to, really. So, as practically always, the problems stem from a combination of factors, and bad programming definitely is one of them.
  - deleted 29d ago
    [deleted]
cookiengineer 29d ago
you are talking about the effect, not the cause. Sites are slow because with all that excess performance they do more tracking, instead of keeping the website as-is. Because that's the only thing business managers can come up with in that situation. It's a misaligned goal of users vs businesses. In my opinion the "user agent" behavior of browsers is long gone, because they're not acting on behalf of their users anymore. They're acting on behalf of businesses.
mark_l_watson 29d ago
I have used Lockdown mode also. Not that inconvenient but I didn’t mind the slight no JIT slowdown. I did find not seeing some images annoying.

by varenc 29d ago

Rohansi 29d ago

It will also increase power consumption because your CPU has to do more work to run the same code.

timr 29d ago

That's largely because a lot of developers have made the devil's bargain of replacing standard web stuff with badly re-implemented JS versions of same. People did it because they could, but never considered if they should. See most of the ecosystem around React, for reference. It's idiotic that things like URL management are done in Javascript. Or form controls. I guarantee that if we stopped doing this kind of stuff, JIT wouldn't matter. To some extent this is just saying "developers will depend upon the performance given to them", and that's true, but it's also true that as soon as things like V8 and Node appeared, JS became ubiquitous. Pandora's container, if you will.

vickychijwani 29d ago
That's largely because a lot of developers have made the devil's bargain of replacing standard hardware and OS primitives with badly re-implemented C versions of same. People did it because they could, but never considered if they should. See most of the ecosystem around modern systems software, for reference. It's idiotic that things like memory layout and bit-level hardware management are done in C abstractions. I guarantee that if we stopped doing this kind of stuff, compiler optimizations wouldn't matter. To some extent this is just saying "developers will depend upon the performance given to them", and that's true, but it's also true that as soon as things like compilers and standard libraries appeared, C became ubiquitous. Pandora's container, if you will.
- timr 29d ago
  > It's idiotic that things like memory layout and bit-level hardware management are done in C abstractions. I guarantee that if we stopped doing this kind of stuff, compiler optimizations wouldn't matter. Cute, but no, not even close to a good metaphor. The C example is abstracting away fundamental complexity in a new platform. The other is completely re-writing -- in duplicate and slightly broken -- what the platform gives you for free. There's nothing about implementing form controls or URL management in JS that is more abstract. It's just different; a downstream bad decision that branches off a long tree of other bad decisions. The equivalent level of idiocy in a C-related metaphor would be...I dunno...if you decided that you didn't like the way that header files worked, and decided to keep the C compiler, but build an external header-file management system in Fortran [1] that calls the C compiler for you. Or even closer to the JS metaphor, you shipped a special C compiler that had an embedded interpreted language that only activated at compile time, and you then used that language to allow any user to fundamentally change the syntax of C. (It hopefully shouldn't be lost on you that this exact approach to language features has been repeatedly tried in the javascript world, including right now, with package management. But see also: typescript, coffeescript before that, Dart, etc. Javascript is a mess, and history repeats itself with regularity about every 5 years.) [1] ...and then you re-write that about sixty times, each time being slightly incompatible with the last, and all having different fundamental incompatibilities with C headers.
grishka 29d ago
> See most of the ecosystem around React, for reference. I've never used React myself, but what I've heard about it makes me question my own sanity. So are you going to tell me that instead of just updating the DOM tree directly I'm going to apply the changes to my data, then pass the entire model to the framework, which would then diff it with the previous version to get the changes back out, it would then call my functions that return components, and it would then diff the virtual DOM to find out what changed, and only then would it update the actual page? Why the fuck would anyone ever want that? What's so hard about simply changing the innerText or inserting elements or whatever? Oh and now Google and Apple are insisting that this is the way to do UIs in native apps as well, with Compose and SwiftUI respectively. The way the front end developer community seems to largely encourage learning top-down isn't helping either. I'll forever remember that one guy we made a small project with. He learned React but had no clue what "send a request" and "pass a parameter" means, and I had to explain him how to use XHR.
- leptons 29d ago
  The DOM is the slowest part of the browser. It's not Javascript, it's the DOM. React is an attempt to manage the slowness of the DOM. One seemingly small change to a page (like setting innerText) can have many ripple effects with reflow on mamy parts of a page. With thousands of DOM elements on a page, the DOM becomes a bottleneck. This isn't the fault of front-end developers, and it's not really the fault of browser developers. HTML/CSS/JS is a very powerful system, but it's also complex and can cost a lot of compute. When you understand this, then the reasons for React and other front-end frameworks become easier to accept.
  - exe34 29d ago
    You may not need react. If you want to make the smallest possible change to the dom to reduce latency, then make the smallest possible change to the dom. Choose solidjs. (Not a sponsored post).
  - grishka 29d ago
    > One seemingly small change to a page (like setting innerText) can have many ripple effects with reflow on mamy parts of a page. I haven't looked into how browsers actually do it, but my mental model for it is that if something changes, this merely sets a flag on that element or its parent that its layout is not valid any more. Then, on next vsync, all the elements that have this flag set have their layout recalculated, potentially going up the tree as necessary. The only exception is if your script tries to get any layout-related property, e.g. offsetWidth. Then, as if as part of the getter of such a property, the layout recalculation will run immediately. That is to say, if you need to make a lot of changes to the DOM, you should make them within one JS invocation so only one layout pass happens sometime after you're done.
tgv 29d ago
The problem is not url management. That should happen just once or twice during the life cycle of a page. If it takes 0.1ms or 1ms doesn't have any impact on the usability. One of my problems was that I wanted to show data in the browser. It is a convenient delivery platform, after all. However, Chrome (and Chrome in particular) has tremendous trouble displaying large pages. A 400x400 table takes a long time to render. I could solve that in JavaScript. I had to, really. So, as practically always, the problems stem from a combination of factors, and bad programming definitely is one of them.
- deleted 29d ago
  [deleted]

cookiengineer 29d ago

you are talking about the effect, not the cause. Sites are slow because with all that excess performance they do more tracking, instead of keeping the website as-is. Because that's the only thing business managers can come up with in that situation. It's a misaligned goal of users vs businesses. In my opinion the "user agent" behavior of browsers is long gone, because they're not acting on behalf of their users anymore. They're acting on behalf of businesses.

mark_l_watson 29d ago

I have used Lockdown mode also. Not that inconvenient but I didn’t mind the slight no JIT slowdown. I did find not seeing some images annoying.