[dtrace-discuss] Detect stack size

[deepti dhokte]

deepti dhokte wrote:
> Casper.Dik at Sun.COM wrote:
>>> why not? as far as I understand, getrlimit and setrlimit are in 
>>> standard C lib as welland they have been used to dynamically get the 
>>> soft an hard
>>> limit of the resources in the context of the current process.
>>>     
>>
>> Yes, but they don't work for the stack size parameters.
>>   
> they work for stack size as well as cpu time,maximum file size, data 
> size, core file size etc.
> are all resources that are allowed to be tuned in the given process's 
> context.
> I recall only use of RLIMIT_STACK resource so far.
I just checked solaris's man page on getrlimit.
apart from typical RLIMIT_STACK and company that are implemented by 
typical unices,
since version 8, Solaris has RLIMIT_AS and RLIMIT_VMEM to increase 
process's total
address space. cool.
-Deepti
>
>> The stack limit determines the area of virtual memory reserved for
>> the stack; 
> agree. stack grows within the allocated virtual memory /process 
> address space for the given process.
>> Solaris maps the lshared libraries directly under it, so
>> it is *impossible* to grow the stack limit for the current process.
>>   
> actually the syscall implementation cares for this detail such as if 
> resource allocation is resulting
> intruding into shared library region or any other region, then further 
> growing of stack size
> would result into error (-1) and stack will not be allowed to be grown 
> (thus setrlimit would return -1
> with errno EINVAL).
> since shared libraries are mapped into one of the processes (and not 
> all) and all other user processes
> keep address of this shared lib, not all processes are giong to have 
> lshared lib in their address space.
>
> so you are right, it is impossible to grow beyond hard limit (hard 
> limits are settable only by su).
> and sucess of setrlimit system call  is limited by per attribute 
> specific hard limit as well total address
> space of the process.
> but still its a better option for processes/theads to efficiently 
> utilize the whatever space available.
>> The thread stacks are mapped at thread started; they are
>> not governed by any stack resource limits .
>>   
> it is implementation dependent. also, threads are initialized with 
> default stack size,
> and newer libs and standards allow threads/processes to tweak these 
> attributes/resources.
> pthread_attr_g/setstacksize and/or  g/setrlimit are useful syscalls.
> -Deepti
>> Casper
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>> dtrace-discuss at opensolaris.org
>>   
>
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