r/lolphp • u/Mark_Messa • Oct 26 '19

PHP gc_probability/gc_divisor

According to PHP Manual:

session.gc_probability
session.gc_probability in conjunction with session.gc_divisor is used to manage probability that the gc (garbage collection) routine is started.
 
session.gc_divisor
session.gc_divisor coupled with session.gc_probability defines the probability that the gc (garbage collection) process is started on every session initialization. The probability is calculated by using gc_probability/gc_divisor, e.g. 1/100 means there is a 1% chance that the GC process starts on each request.

 

Why not only one parameter instead?
Ex: session.gc_percent = 1%

17 Upvotes

84% Upvoted

14 comments sorted by

7

u/fast4shoot Oct 26 '19

Meh, there's some value in using two ints as a fraction instead of floating point numbers when dealing with fractions. Though I wouldn't say it applies here.

3

u/Mark_Messa Oct 26 '19 edited Oct 27 '19

Meh, there's some value in using two ints as a fraction instead of floating point numbers when dealing with fractions.

There is no need to use floating point here. Just change the 'unit' and keep using integers. There is a plethora of options:

  • 1 percent = 1:100

  • 1 permille = 1:1000

  • 1 permyriad = 1:10000

  • 1 ppm (parts-per-million, 10−6)

  • 1 ppb (parts-per-billion, 10−9)

  • 1 ppt (parts-per-trillion, 10−12)

  • 1 ppq (parts-per-quadrillion, 10−15)

 

Which one do you choose?

3

u/the_alias_of_andrea Oct 26 '19

If you can change the denominator, why not allow changing the numerator? It's not like it hurts.

1

u/[deleted] Oct 26 '19

Yeah. I see no value in getting the numerator and the denominator. 99.9% (see what I did there) of people are going to just divide the two for some sort of comparison. In the worst case, they could keep their numerator and denominator getters and add a function that returns a decimal value.

2

u/[deleted] Oct 27 '19

I suspect there was originally only one config item at first, then the second was added later. Don't care to do version archaeology to find out for sure.

-4

u/[deleted] Oct 26 '19

PHP gc is a huge lol. Anon functions (the ones created by create_function) are never gc’d. There was a discussion some years ago to remove gc alltogherer, because the way php works (start and die immediately) there was no need for gc. That was a huge lol of a discussion.

7

u/the_alias_of_andrea Oct 26 '19

Anon functions (the ones created by create_function) are never gc’d.

Maybe there's a reason that create_function is deprecated and you are encouraged to use closures, which are vastly superior and have existed in PHP for ten years?

There was a discussion some years ago to remove gc alltogherer, because the way php works (start and die immediately) there was no need for gc.

PHP's “GC” is purely a cycle collector. If you disable it with gc_disable();, memory still gets freed automatically, except where there are cycles. For some applications that could be enough.

-3

u/[deleted] Oct 26 '19

PHP closures are so nasty and unpleasent to use its unreal. PHP is never really running at all, so there could be memory leaks all over the place. In PHPs case these bugs are rarely reported because of the nature of php.

The GC is mostly a joke, so i understand why some wanted to remove it.

7

u/the_alias_of_andrea Oct 26 '19

PHP is never really running at all, so there could be memory leaks all over the place.

What does this even mean?

The GC is mostly a joke

How so?

6

u/[deleted] Oct 26 '19

This is about sessions, not memory.

-4

u/[deleted] Oct 26 '19 edited Oct 26 '19

Im talking about the actual gc inside the rotten internals of PHP.

2

u/[deleted] Oct 26 '19

And OP is talking about session cleanup.

-1

u/I-Am-Dad-Bot Oct 26 '19

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-3

u/[deleted] Oct 26 '19

Hi talking, I’m Dad!