Somehow I can allocate up to 95ish GB of ram but where is that memory coming from? My computer isn't even using all its ram as expected and my storage doesn't seem to decrease at all either. What's going on?
#Allocating more RAM than available
signal folio
sturdy hamletBOT
signal folio
my code: c int count = 0; while(1) { int *p = malloc(ONEGB); if (p == NULL) { printf("malloc refused after %d Gb\n", count); return 0; } memset(p,1,ONEGB); printf("got %d GB\n", ++count); if (count == 95) while(1); }
i have the while loop set at count == 95 because it just crashes afterwards and the (p == NULL) isn't even run (or at least it doesn't print and return 0)
gloomy fable
Often times windows will let you store temp ram on a drive. Its not fast and it causes stuttering, but for chrome or something its better than not storing data. P.s. This is my guess based on my overclocking experiences.
signal folio
ic. The only thing is that it doesn't look like my drive memory is increasing but idk
heady imp
Often times windows will let you store temp ram on a drive. Its not fast and it ...
You do notice that ain't Windows right?
gloomy fable
Yea, but was just giving a reference @heady imp
Again, only from my experience with a windows operating system
Could be doign the same thing though
heady imp
Somehow I can allocate up to 95ish GB of ram but where is that memory coming fro...
Try looking at the compressed amount.
feral hinge
Somehow I can allocate up to 95ish GB of ram but where is that memory coming fro...
what is this even a screenshot of
a.out - 95 GB
what are you taking a picture of
did you do like an ls or something
signal folio
did you do like an ls or something
activity monitor
showing how much ram the process is using
feral hinge
i think maybe what happened is a memory leak
i don't know the implementation of the c standard library or what software chain is involved in the activity monitor or what it is pulling from the OS or what the OS is keeping track of
but your program clearly is written to leak one gigabyte of memory every iteration of that looo
signal folio
i mean the point is to fill up as much mem as i can
feral hinge
i understand
but I'm wondering if somehwere in this software chain something is not being updated due to the memory leak and something else is tricking something else
IDK
signal folio
idk
feral hinge
it could be that something is optimizing and recognizing that memory is no longer used and something else doesn't know which is why there's a disconnect
feral hinge
that's what I meant before
i explained it badly
you could try to use a debugger to see also
are you familiar with gdb
the picture disappeared
anyways this might be a bug in something in the OS or library for something tbh
feral hinge
well maybe you don't need to use gdb if you don't know it but instead you can edit the program to store these pointers to a global array of pointers and then after the 95 loops run you can do another 95 loops checking the contents and printing the pointer to see if there's any funny business
feral hinge
and in case something is optimizing it out because you don't use it ever, then it would crash because now you use it
heady imp
Try looking at the compressed amount.
Well did you do this?
signal folio
Well did you do this?
not yet b/c i have to run the program again but the compressed amount for the ram is in the screen shot
signal folio
ok well tbh what I just said it's what I would do before gdb now
ok
heady imp
I want you to watch it as the program runs.
signal folio
ok
signal folio
I want you to watch it as the program runs.
yea it grew by .3 GB if any
heady imp
So that might be where your memory is.
signal folio
yea but how is it supposed to hold multiple gigs
heady imp
Your data is all uniform.
cunning dragon
I have a theory: Generally speaking, at least in my case, allocating more memory than physically available is impossible. However, OS have the ability to extend the memory by virtually increasing the RAM which involves using the drive memory. So, although malloc can only use the heap to dynamically store memory, the OS kernel can do whatever it wants to. So, your app is using that ammount of space because you did not use the free() function to deallocate the memory. This is called memory leak. And it is not showing the printf message because the OS is populating the drive memory once the heap is full. So it allwyas returns a non-nullptr.
signal folio
yea but i don't see drive mem increase? unless it doesn't show that
prime wing
ic. The only thing is that it doesn't look like my drive memory is increasing bu...
well the swap file will normall already exist and have a fixed size
that's assuming you have a swap file and not a swap partition
is it swap file or swapfile? idk
sturdy hamletBOT
@signal folio Has your question been resolved? If so, run !solved :)
signal folio
!solved
sturdy hamletBOT
signal folio
:)_ _
olive comet
cunning dragon
Anyways @signal folio, please remember to allways free the allocated memory once it is not necessary anymore. Otherwise, the system will keep certain chunks of data reserved that are not being used! It has been a pleasure helping you out!