Garbage collector

  • Thread starter Eustáquio Rangel de Oliveira Jr.
  • Start date
E

Eustáquio Rangel de Oliveira Jr.

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Hi!

Hey, how often the garbage collector runs?
When all the memory becomes full?
Or there is a pre-defined interval?

And, do you have some links about the the Ruby mark-and-sweep type of
garbage?

Thanks! :)

- ----------------------------
Eustáquio "TaQ" Rangel
(e-mail address removed)
http://beam.to/taq
Usuário GNU/Linux no. 224050
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B

Bill Atkins

It runs when Ruby runs out of memory or when it's manually invoked (by
ObjectSpace.garbage_collect or GC.start).

Bill
 
C

Charles Mills

Eustáquio Rangel de Oliveira Jr. said:
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Hash: SHA1

Hi!

Hey, how often the garbage collector runs?
When all the memory becomes full?
Or there is a pre-defined interval?
It basically runs when a certain amount of memory is used - see
malloc_increase and malloc_limit in gc.c. Also, if malloc() fails or
attempts to open a file fail do to memory limitations the gc will be
run.

And, do you have some links about the the Ruby mark-and-sweep type of
garbage?
http://www.rubygarden.org/ruby?GCAndMemoryManagement
http://www.rubygarden.org/ruby?GCAndExtensions

-Charlie
 
G

gabriele renzi

Eustáquio Rangel de Oliveira Jr. ha scritto:
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Hash: SHA1

Hi!

Hey, how often the garbage collector runs?
When all the memory becomes full?
Or there is a pre-defined interval?

And, do you have some links about the the Ruby mark-and-sweep type of
garbage?

Thanks! :)

btw, I thought 1.9 could see the light of a different GC.. Is someone
working on that or is it something still very far in the future?
 
M

Martin Pirker

Eustáquio Rangel de Oliveira Jr. said:
And, do you have some links about the the Ruby mark-and-sweep type of
garbage?

While I lack the skill to go source diving, I too am interested in more
info about the gc.
We use conservative gc [talk:102873], ok

So, can one help gc?
e.g. if an Array or Hash is no longer needed, does an Array.clear or
Hash.clear actually zero all internal pointers to help/speed up gc?

How much extra memory does every Ruby object allocation take?
Any alignment losses?

Is there e.g. a preallocate for a String - if I know it'll grow to ~10kb
by using << and I don't want to produce so much temp garbage?


Martin
 
M

Michael Neumann

Martin said:
Eustáquio Rangel de Oliveira Jr. said:
And, do you have some links about the the Ruby mark-and-sweep type of
garbage?


While I lack the skill to go source diving, I too am interested in more
info about the gc.
We use conservative gc [talk:102873], ok

So, can one help gc?
e.g. if an Array or Hash is no longer needed, does an Array.clear or
Hash.clear actually zero all internal pointers to help/speed up gc?

Yes, that should help, as the mark function would no more mark all the
value. But I doubt that would be much of a performance win, because if
the array-object goes out of scope (it's no more reachable), it's mark
function would no longer be called. So, you would not want to call
#clear. But that's just my understanding...

Regards,

Michael
 
L

Lothar Scholz

Hello Michael,

MN> Martin Pirker said:
Eustáquio Rangel de Oliveira Jr. said:
And, do you have some links about the the Ruby mark-and-sweep type of
garbage?


While I lack the skill to go source diving, I too am interested in more
info about the gc.
We use conservative gc [talk:102873], ok

So, can one help gc?
e.g. if an Array or Hash is no longer needed, does an Array.clear or
Hash.clear actually zero all internal pointers to help/speed up gc?

MN> Yes, that should help, as the mark function would no more mark all the
MN> value. But I doubt that would be much of a performance win, because if
MN> the array-object goes out of scope (it's no more reachable), it's mark
MN> function would no longer be called. So, you would not want to call
MN> #clear. But that's just my understanding...

This would only help if there is something on the stack that looks
like an address to this array object. The chance for this is very low
and so the performance win. With the Boehm-Weisser GC i a measurable
memory reduction (~20%) by doing this for eiffel. But Boehm-Weisser
scans everything conservative and not only the heap like ruby.
 
M

Michael Neumann

Lothar said:
Hello Michael,

MN> Martin Pirker said:
And, do you have some links about the the Ruby mark-and-sweep type of
garbage?


While I lack the skill to go source diving, I too am interested in more
info about the gc.
We use conservative gc [talk:102873], ok

So, can one help gc?
e.g. if an Array or Hash is no longer needed, does an Array.clear or
Hash.clear actually zero all internal pointers to help/speed up gc?


MN> Yes, that should help, as the mark function would no more mark all the
MN> value. But I doubt that would be much of a performance win, because if
MN> the array-object goes out of scope (it's no more reachable), it's mark
MN> function would no longer be called. So, you would not want to call
MN> #clear. But that's just my understanding...

This would only help if there is something on the stack that looks
like an address to this array object. The chance for this is very low
and so the performance win. With the Boehm-Weisser GC i a measurable
memory reduction (~20%) by doing this for eiffel. But Boehm-Weisser
scans everything conservative and not only the heap like ruby.

Hm, my understanding of Ruby's GC is that it scans the stack
conservative (meaning that all values on the stack that look like
references to memory are handled as references), but not the heap (how
could you conservativly scan the heap?). But probably I misunderstood you.

And my final conclusion was that it does not help much, if any, despite
my initial "Yes" ;-)

Regards,

Michael
 
L

Lothar Scholz

Hello Michael,

MN> Hm, my understanding of Ruby's GC is that it scans the stack
MN> conservative (meaning that all values on the stack that look like
MN> references to memory are handled as references), but not the heap (how
MN> could you conservativly scan the heap?). But probably I misunderstood you.

Yes. It was a typo i meant "not only the stack like ruby".
Sorry for the confusion.
 

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