HP-UX Reference (11i v2 07/12) - 3 Library Functions N-Z (vol 7)

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pthread_default_stacksize_np(3T) pthread_default_stacksize_np(3T)

(Pthread Library)

NAME

pthread_default_stacksize_np() - change the default stacksize.

SYNOPSIS

#include <pthread.h>

int pthread_default_stacksize_np(

size_t new_size,

size_t *old_size

);

PARAMETERS

new_size The new default stack size.

old_size Pointer to where the old default stack size is returned.

DESCRIPTION

The pthread_default_stacksize_np()

function allows an application to change the default value

for the stacksize attribute. This function must be called before any threads have been created. The new

default stack size is passed in the new_size parameter. If not

NULL, the previous default stack size is

returned in old_size.Ifnew_size is zero, this function can be used (at any time) to query the current

default stack size.

On HP-UX, threads with default stack sizes are cached after they terminate. The next time a thread is

created with a default stack size, a cached thread (and its stack) are reused. This can result in signiﬁcant

performance improvements for pthread_create()

However, if the default stack size is not appropriate for an application, it cannot take advantage of this per-

formance enhancement. By using the

pthread_default_stacksize_np()

function, the threads

library will change the default stack size so that it matches the applications needs. This allows the applica-

tion to utilize the performance beneﬁt of cached threads.

WARNING

If the environment variable

PTHREAD_DEFAULT_STACK_SIZE

is set with valid value for default stack

size, then it takes precedence over the invocation of the

pthread_default_stacksize_np()

inter-

face. However, it returns current default stack size in old_size. Also, the maximum default stack size value

that can be set through

PTHREAD_DEFAULT_STACK_SIZE

environment variable is restricted to 10 MB

and any value above the same will be rounded off to 10 MB. Care should be taken while setting the default

stack size limits as this could impact the maximum number of threads that can be created in a process.

RETURN VALUE

Upon successful completion,

pthread_default_stacksize_np()

returns zero. Otherwise, an error

number is returned to indicate the error (the

errno variable is not set).

ERRORS

If any of the following occur, the pthread_default_stacksize_np()

function returns the

corresponding error number:

[EINVAL] The value speciﬁed by new_size is less than

PTHREAD_STACK_MIN

[EPERM] The calling process has already created threads (this must be called before any

threads are created).

AUTHOR

pthread_default_stacksize_np() was developed by HP.