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0 pointsaustin-cheney7mo ago0 comments

This is exactly what I am talking about. All these excuses, especially about vanity, are masking behaviors.

DOM access is not quite as fast now as it was 10 years ago. In Firefox I was getting just under a billion operations per second when perf testing on hardware with slow DDR3 memory. People with more modern hardware were getting closer to 5 billion ops/second. That isn’t slow.

Chrome has always been much slower. Back then I was getting closer to a max of 50 million ops/second perf testing the DOM. Now Chrome is about half that fast, but their string interpolation of query strings is about 10x faster.

The only real performance problem is the JS developer doing stupid shit.

0 comments

jerf7mo ago

"In Firefox I was getting just under a billion operations per second when perf testing on hardware with slow DDR3 memory."

When you profile something and you get "a billion per second" what you've got there is a loop where the body has been entirely optimized away. Presumably the JIT noticed you were doing nothing and making no changes and optimized it away. I don't think there's a single real DOM operation you can do in an amortized 3-ish CPU cycles per operation (2015 3GHz-ish CPU, but even at 5GHz it wouldn't matter).

That's not a real performance number and you won't be seeing any real DOM operations being done at a billion per second anytime soon.

austin-cheneyOP7mo ago

Or, more likely, it’s a traversal of a data structure already in memory. If so, then it is a very real operation executing as fast as reported, at near memory speed.

jerf7mo ago

You can't even "traverse" a data structure at that speed. We're talking low-single-digit cycles here. A compiled for loop tends to require two cycles just to loop (you need to increment, compare, and jump back but the CPU can speculate the loop will in fact jump back so the three operations can take two cycles), and I don't know what the minimum for a JS-engine JIT'd loop is but needing 4 or 5 wouldn't stun me. That's literally the "compiled loop do-nothing speed".

I mention this and underline it because this is really an honorary "latency value every programmer should know"; I've encountered this multiple times online where someone thought they were benchmarking something but they didn't think about the fact that .6 nanoseconds per iteration comes out to about 2-3 cycles (depending on CPU speed) and there's no way what they thought was benchmarking could be done that quickly, and I've now encountered it twice at work. It's a think worth knowing.

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troupo7mo ago

> All these excuses, especially about vanity, are masking behaviors.

1. These are not excuses, these are facts of life

2. No idea where you got vanity from

> DOM access is not quite as fast now as it was 10 years ago. I was getting just under a billion operations per second

Who said anything about DOM access?

> The only real performance problem is the JS developer doing stupid shit.

Ah yes. I didn't know that "animating a simple rectangle requires 60% CPU" is "developers doing stupid shit" and not DOM being slow because you could do meaningless "DOM access" billions time a second.

Please re-read what I wrote and make a good faith attempt to understand it. Overcome your bias and foregone conclusions.

j / k navigate · click thread line to collapse

0 pointsaustin-cheney7mo ago0 comments

This is exactly what I am talking about. All these excuses, especially about vanity, are masking behaviors.

The only real performance problem is the JS developer doing stupid shit.

0 comments

jerf7mo ago

"In Firefox I was getting just under a billion operations per second when perf testing on hardware with slow DDR3 memory."

That's not a real performance number and you won't be seeing any real DOM operations being done at a billion per second anytime soon.

austin-cheneyOP7mo ago

Or, more likely, it’s a traversal of a data structure already in memory. If so, then it is a very real operation executing as fast as reported, at near memory speed.

jerf7mo ago

1 more reply

troupo7mo ago

> All these excuses, especially about vanity, are masking behaviors.

1. These are not excuses, these are facts of life

2. No idea where you got vanity from

> DOM access is not quite as fast now as it was 10 years ago. I was getting just under a billion operations per second

Who said anything about DOM access?

> The only real performance problem is the JS developer doing stupid shit.

Please re-read what I wrote and make a good faith attempt to understand it. Overcome your bias and foregone conclusions.

j / k navigate · click thread line to collapse