4 ms·

Google Speed Tips Get Picked Apart

20 points by AndrewWarner 17y ago

chaosmachine 17y ago
Glad to see I'm not the only one who thought those PHP tips were more than a little suspect... GOOD: echo $_POST['description']; That really should not have made it past their editorial process.
- smokinn 17y ago
  That example was particularly egregious. PHP uses copy-on-write so the temp variable held a pointer to the 500k of data they mentioned, not a copy. Had they concatenated a small string to the end then PHP wouldn't copied the data and used the MB of memory they alluded to. That whole document was half baked at best. EDIT: I went to look at the document to reference the example and noticed that they changed their example. It used to be: $description = $_POST['description']; echo $description; And now it's: In the following example, imagine if a malicious user had inserted 512KB worth of characters into a textarea field. This would result in 1MB of memory being used! $description = strip_tags($_POST['description']); echo $description; There's no reason to copy the variable above, you can simply do this operation inline and avoid the extra memory consumption: echo strip_tags($_POST['description']); So someone is definitely working on making the examples at least match the description.
grandalf 17y ago
I like the feature of assessing slow CSS. I'd never realized that constructs like the following would be "very inefficient": #foo p span{ color: #fff; }
- apsurd 17y ago
  i read it, but still have to ask why ?
  - grandalf 17y ago
    why they're inefficient?
  - dezwald 17y ago
    it's inefficient because the browser has to search/loop through the DOM looking for the exact pattern of the corresponding css rules, instead of a direct pointer like: #my_foo_span{ color:#fff }.
    - jonhohle 17y ago
      but they mean different things. one says, all spans which are descendants of divs which are descendants of some elements with id=foo. the other says one element with id=my_foo_span. duplicating rules in CSS to match overly specific IDs defeats one of its major advantages.
    - grandalf 17y ago
      one thing I don't understand is, does that mean it's bad CSS style? Is doing the suggested optimization equivalent to writing really huge functions in c before compilers could inline?

20 points by AndrewWarner 17y ago

Glad to see I'm not the only one who thought those PHP tips were more than a little suspect... GOOD: echo $_POST['description']; That really should not have made it past their editorial process.

smokinn 17y ago
That example was particularly egregious. PHP uses copy-on-write so the temp variable held a pointer to the 500k of data they mentioned, not a copy. Had they concatenated a small string to the end then PHP wouldn't copied the data and used the MB of memory they alluded to. That whole document was half baked at best. EDIT: I went to look at the document to reference the example and noticed that they changed their example. It used to be: $description = $_POST['description']; echo $description; And now it's: In the following example, imagine if a malicious user had inserted 512KB worth of characters into a textarea field. This would result in 1MB of memory being used! $description = strip_tags($_POST['description']); echo $description; There's no reason to copy the variable above, you can simply do this operation inline and avoid the extra memory consumption: echo strip_tags($_POST['description']); So someone is definitely working on making the examples at least match the description.

grandalf 17y ago

I like the feature of assessing slow CSS. I'd never realized that constructs like the following would be "very inefficient": #foo p span{ color: #fff; }

apsurd 17y ago
i read it, but still have to ask why ?
- grandalf 17y ago
  why they're inefficient?
- dezwald 17y ago
  it's inefficient because the browser has to search/loop through the DOM looking for the exact pattern of the corresponding css rules, instead of a direct pointer like: #my_foo_span{ color:#fff }.
  - jonhohle 17y ago
    but they mean different things. one says, all spans which are descendants of divs which are descendants of some elements with id=foo. the other says one element with id=my_foo_span. duplicating rules in CSS to match overly specific IDs defeats one of its major advantages.
  - grandalf 17y ago
    one thing I don't understand is, does that mean it's bad CSS style? Is doing the suggested optimization equivalent to writing really huge functions in c before compilers could inline?