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I'm the one with the app that has been running on server for a long time (many years).
No out of memory errors.
Other comes along and has out of memory errors then thinks it's someone else.
Kind of annoying. I'm mostly just curious, because my main point is that "you can't really entirely effect another process (this would be almost like a malicious process which could cause another app to fault)" because your app is stuck in it's own address space.
Now if the server has 4GB memory then yes maybe my app taking memory could cause you issue since neither of us really has the correct amount of space.
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raddevus wrote: gets an address space which is 4GB in size when the process starts
I'm not sure about the actual limit, but I don't think it's a low cap like that per process... maybe per thread. I dunno. Gonna have to check out obermd's link myself.
raddevus wrote: OS modules take up certain portion of that address space (1GB?)
Not from an application's perspective. That died out in the Win31 days. These days just about every OS uses a ring architecture, where 0 is the highest access and is usually only accessed by the kernel. Applications have the least amount of access into something called protected memory, which virtually maps addresses to make your app think it can access whatever, but it can't.
You'll never accidently overwrite the OS' memory these days, but you can have a memory leak and take the system down that way.
raddevus wrote: The rest (3GB) is used for the stack & heap of the running process
For an application, there are 3 areas of memory: static, stack, and heap. Stack and heap get all the attention, but static is just as important. Static memory is used for things like literals that is embedded in the application itself. For instance:
const char *howdy (void) {
return "Howdy";
}
int main()
{
printf("%s\n", howdy());
return 0;
}
This is perfectly valid C code. The string "howdy" can be found in a hex editor and stored in the executable itself. Unlike stack memory it's not going to get wiped out so easy, which means you can return a pointer to it directly in a function. You copy that literal over to a local variable on the stack though and return the variable, well things will start breaking if you did that.
raddevus wrote: As the app instantiates new objects (allocates memory for objects) on the heap, the amount of memory the process uses grows -- but it can never grow beyond the 3GB (4GB total) anyways, right?
Depends. The whole idea behind swap (*nix) or page files (Windows) is to get around that. The OS would extend the memory be moving things in and out of disk. Slow as dirt and not used these days nearly as much. But, if swap/paging is disabled then yes.
raddevus wrote: 5 ## This is a biggie ## A process can never eat up more memory than its address space allows 3GB (4GB total) so a process can never really impact another process anyways because each one is limited to 4GB anyways, right?
Correct, in a protected memory model. So, stay away from Win31.  I don't think the exact limit is 3GB again, but an app can only screw up its own memory. However, if it does have a memory leak it could make it impossible for other apps to allocate memory and you get a crash that way. But, their memory won't be corrupted unless there's a bug in the other app somewhere.
raddevus wrote: 6. Extreme Example - If there is 128GB RAM in the hardware and we say OS (associated services) take up 28GB (to make things easy) and there are two services running (2 X 4GB = 8GB) then this machine could never run out of memory, since it would have 92GB just sitting idle
Assuming there's no memory leaks/bugs, yeah.
raddevus wrote: Driving A Point Home - So when a developer notices that the app he wrote running on the Server keeps crashing with "out of memory" error, then looks around and says, "Hey, wait a second, I think your service (which has been running on the Server long before aforementioned dev's app) is eating up memory and making mine die", then that developer is an idiot who doesn't understand process address space, right? Right? Right!
It depends. Could be, your app. Could be another app. You don't have to guess though. Every OS on the planet will tell you which processes are using the most memory. If it's Linux use top or install htop and find out. You can also write a script to monitor them.
raddevus wrote: You cannot solve memory problems of a service or app that crashes due to low memory (since it is simply eating it's own memory) by installing more memory (even if hardware is furhter expandable).
Depends on the nature of the bug in the service.
Jeremy Falcon
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I've overstated many things.
My point is that a single process cannot just consume all memory on a box, right?
It's limited to some address space size, I'm guessing.
But, maybe I'm wrong, maybe a process can consume all 128GB of ram??
That's what I'm really curious about.
I think it cannot becuase it would be quite easy for a malicious process to crash other processes and the OS if this were true.
When a process gets memory from heap (for newing up objects) it gets it from its own address space. When that memory is gone then you get "out of memory" but doesn't mean you ate all the memory on the box.
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raddevus wrote: My point is that a single process cannot just consume all memory on a box, right?
I already mentioned this... It's only available memory not already claimed. It's first come, first serve. So, assuming you're 64-bit and have less than 8TB memory then it can consume all the remaining available memory. Just like disks though, memory should never be "full" or else you'll run into problems.
raddevus wrote: It's limited to some address space size, I'm guessing.
Obermd posted the limits. My reply was about how memory works, so between the two of these you should know the limits.
raddevus wrote: But, maybe I'm wrong, maybe a process can consume all 128GB of ram??
Again, the OS will use some. Some graphics cards may also use some. Your app will never have access to that. It's available memory it can consume. I took time to write that reply, please go through it.
raddevus wrote: I think it cannot becuase it would be quite easy for a malicious process to crash other processes and the OS if this were true.
Nobody ever said otherwise. You asked if it could, all of us said no and I gave a detailed explanation of why not.
raddevus wrote: When a process gets memory from heap (for newing up objects) it gets it from its own address space. When that memory is gone then you get "out of memory" but doesn't mean you ate all the memory on the box.
Again, I already talked about protected/virtual memory. Did you read my reply?
Jeremy Falcon
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Oh, I read. I was just confused.
It often takes me a long while to understand things.
I'm a very slow developer. I've worked in IT for > 33 years & dev around 25 but I'm still honestly slow.
Just takes me a while to understand concepts.
That's it. Thanks for your help. I'll read it again.  
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Thanks for the honesty buddy.  We all have our thing. Like my biggest weakness is impatience (some might say being a douche ).
Jeremy Falcon
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1 2 and 3 are true of 32-bit processes. I don't think it's true of 64 bit processes.
Check out my IoT graphics library here:
https://honeythecodewitch.com/gfx
And my IoT UI/User Experience library here:
https://honeythecodewitch.com/uix
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Yeah, I'm very curious if a process can allocate memory beyond 3-4GB size.
I saw a thing that made it look like it could :
384 GB or system commit limit, whichever is smaller Windows 8.1 and Windows Server 2012 R2: 15.5 TB or system commit limit, whichever is smaller.
But that seems terribly dangerous. But what do I know.
Also, interested in what "system commit limit" is and if that is still set to 3-4GB on 64 bit processes.
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System commit limit sounds like it might be the amount of dirty memory it can write to the swap, or maybe that it can use as swap? Not sure, but I'm more inclined to think it's the former rather than the latter, if any.
Edit: I'm surprised it wouldn't be expressed in pages rather than GB though.
Check out my IoT graphics library here:
https://honeythecodewitch.com/gfx
And my IoT UI/User Experience library here:
https://honeythecodewitch.com/uix
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Step away from the misbehaving application for a moment. Fire up a VM running the Windows OS you want, and write a bad, evil application. It does not have to be complex. Using a VM allows you to crash/hang it instead of your main box. Try malloc (comes off the heap) and static allocation (process space?). I'm rusty. Just play around.
That said, trust nothing Microsoft "documents." I fully confess that I am jaded. Trust but verify.
I have had my left leg in the embedded world and the right leg on the desktop. My two common errors has been buffer overflows into malloc'd areas and stack overflows. Either way, it's an application issue.
Keep learning.
Charlie Gilley
βThey who can give up essential liberty to obtain a little temporary safety deserve neither liberty nor safety.β BF, 1759
Has never been more appropriate.
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I need to amend my earlier statement about 32-bit processes under Windows.
While it's not important, historically the process address space was divvied such that the lower 2GB was "user space" and the upper 2GB was "kernel space" (I may have that backward, but either way, it's half and half)
Some apps could be "3GB aware", sometimes run with a command line switch like /3GB to enable it. In that case, the kernel was only mapped to 1GB of the address space. I'm not sure why all apps weren't this way, other than compatibility. An example of a 32 process that could be 3GB aware with a command line switch is the old 32-bit versions of Image Line's FL Studio DAW software.
Check out my IoT graphics library here:
https://honeythecodewitch.com/gfx
And my IoT UI/User Experience library here:
https://honeythecodewitch.com/uix
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For Linux and friends, start with man getrlimit and apropos oom. The whole OOM-killer environment is intriguing, to say the least. I believe it came from the *nix legacy of lots of users timesharing a machine with limited resources, particularly memory. A competitive, rather than cooperative, workload.
Software rusts. Simon Stephenson, ca 1994. So does this signature. me, 2012
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"A little time, a little trouble, your better day"
Badfinger
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"I have no idea what I did, but I'm taking full credit for it." - ThisOldTony
"Common sense is so rare these days, it should be classified as a super power" - Random T-shirt
AntiTwitter: @DalekDave is now a follower!
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In a closed society where everybody's guilty, the only crime is getting caught. In a world of thieves, the only final sin is stupidity. - Hunter S Thompson - RIP
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Happiness will never come to those who fail to appreciate what they already have. -Anon
And those who were seen dancing were thought to be insane by those who could not hear the music. -Frederick Nietzsche
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Ok, I have had my coffee, so you can all come out now!
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Within you lies the power for good - Use it!
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I'm the kind of stuck that doesn't resolve itself to a programming question.
As an adult I used to work with someone I taught coding to back when we were teens, and we'd buddy code, and accomplish things neither one of us could do on our own. We worked really well together.
Eventually he went off to NYC to make obscene amounts of money.
But that's the kind of help I need. This SVG stuff is absolutely kicking my ass.
Check out my IoT graphics library here:
https://honeythecodewitch.com/gfx
And my IoT UI/User Experience library here:
https://honeythecodewitch.com/uix
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honey the codewitch wrote: off to NYC to make obscene amounts of money
Sorry, can't help you there. 
Freedom is the freedom to say that two plus two make four. If that is granted, all else follows.
-- 6079 Smith W.
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Quote: [...] obscene amounts of money.
honey the codewitch wrote: [...] that's the kind of help I need.
Me too.
On the serious side, I strongly doubt the magician would happen again.
"In testa che avete, Signor di Ceprano?"
-- Rigoletto
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