FWIW, `MAP_PRIVATE|MAP_ANONYMOUS|MAP_POPULATE` would've done the same job.
System CPU Usage and Glibc
21–24 of 24 posts
Re: System CPU Usage and Glibc
#22Earlier quoted context omitted.
What change in behavior? "v7-style" fork is still used in modern POSIX, and most definitely in HPC/industrial/academic software. If you have no use for threads sharing memory, that is. If any libc is translating fork() calls into pseudo-equivalents of "vfork" then that libc is just not-POSIX.
It is not vfork, it is similar to rfork in FreeBSD but note that fork(), vfork(), and __clone() all invoke clone() in Linux post 2.4. The costs of copying the parent tables and creating the task is the only additional cost for fork(), which is very different than the didactic explanation of fork()+exec(). https://man7.org/linux/man-pages/man2/fork.2.html "C library/kernel differences Since version 2.3.3, rather than…
If you look in the glibc source code in `sysdeps/unix/sysv/linux/arch-fork.h` you will see how it is calling clone BTW.
In Linux really threads are just tasks that share memory and processes are tasks that do not.
fork() and pthread_create() simply end up in the same place because user threads or processes are just tasks to the kernel.
Kernel threads, which are not user space are different.
https://github.com/torvalds/linux/blob/master/include/linux/...
The sched wouldn't be able to use a Red-Black trees in the way it does if it didn't
Re: System CPU Usage and Glibc
#23Earlier quoted context omitted.
What change in behavior? "v7-style" fork is still used in modern POSIX, and most definitely in HPC/industrial/academic software. If you have no use for threads sharing memory, that is. If any libc is translating fork() calls into pseudo-equivalents of "vfork" then that libc is just not-POSIX.
It is not vfork, it is similar to rfork in FreeBSD but note that fork(), vfork(), and __clone() all invoke clone() in Linux post 2.4. The costs of copying the parent tables and creating the task is the only additional cost for fork(), which is very different than the didactic explanation of fork()+exec(). https://man7.org/linux/man-pages/man2/fork.2.html "C library/kernel differences Since version 2.3.3, rather than…
So there is no change in visible behavior, it is just an implementation detail.
Re: System CPU Usage and Glibc
#24Earlier quoted context omitted.
It is not vfork, it is similar to rfork in FreeBSD but note that fork(), vfork(), and __clone() all invoke clone() in Linux post 2.4. The costs of copying the parent tables and creating the task is the only additional cost for fork(), which is very different than the didactic explanation of fork()+exec(). https://man7.org/linux/man-pages/man2/fork.2.html "C library/kernel differences Since version 2.3.3, rather than…
So there is no change in visible behavior, it is just an implementation detail.
A very important implementation detail if you are digging into the kernel due to performance problems like in the OP.
But yes, in the naive user perspective case the contract hasn't been violated.