Этот пост не про то, как правильно писать программы плодя чайлды, а про то, что делает системный вызов fork (именно про него спрашивают чаще всего на собесах админов, а не про vfork, не про clone, и не про posix_spawn). Но я с удовольствием прочитаю вашу статью на эту тему. Тема, безусловно, интересная.
Historic description
Under Linux, fork(2) is implemented using copy-on-write pages, so the
only penalty incurred by fork(2) is the time and memory required to
duplicate the parent's page tables, and to create a unique task
structure for the child. However, in the bad old days a fork(2)
would require making a complete copy of the caller's data space,
often needlessly, since usually immediately afterward an exec(3) is
done. Thus, for greater efficiency, BSD introduced the vfork()
system call, which did not fully copy the address space of the parent
process, but borrowed the parent's memory and thread of control until
a call to execve(2) or an exit occurred. The parent process was
suspended while the child was using its resources. The use of
vfork() was tricky: for example, not modifying data in the parent
process depended on knowing which variables were held in a register.
Коллеги, если посмотреть тот же man fd_set, то:
select() has no sigmask argument, and behaves as pselect() called with NULL sigmask.
Описывал я select, а pselect использовал, так как в свежем ядре он заменил select. Суть статьи была не в этом. Но в любом случае спасибо, что читаете. Все комментарии выше относятся к pselect, который используется в исходниках.
Historic description
Under Linux, fork(2) is implemented using copy-on-write pages, so the
only penalty incurred by fork(2) is the time and memory required to
duplicate the parent's page tables, and to create a unique task
structure for the child. However, in the bad old days a fork(2)
would require making a complete copy of the caller's data space,
often needlessly, since usually immediately afterward an exec(3) is
done. Thus, for greater efficiency, BSD introduced the vfork()
system call, which did not fully copy the address space of the parent
process, but borrowed the parent's memory and thread of control until
a call to execve(2) or an exit occurred. The parent process was
suspended while the child was using its resources. The use of
vfork() was tricky: for example, not modifying data in the parent
process depended on knowing which variables were held in a register.
select() has no sigmask argument, and behaves as pselect() called with NULL sigmask.
Описывал я select, а pselect использовал, так как в свежем ядре он заменил select. Суть статьи была не в этом. Но в любом случае спасибо, что читаете. Все комментарии выше относятся к pselect, который используется в исходниках.