41–50 of 358 posts
This seems unnecessary to me. In the example, the core of git should be a library yo can link so you don't need to run the binary. That would be better in every way.
There are lots of reasons to want to spawn fresh processes, which aren't solved by linking a library.
The elegance of the fork() + exec() model is that every kind of configuration can be done after the fork using all the usual APIs. Every attempt to replace it with a combined call that I have seen so far seemed fundamentally poorer because it needs to add all configuration options as parameters to the call and then do this in away that you can extend it later and does not become a mess.
I have the entirely opposite opinion. IMO a big mistake of the UNIXy model is that so much state is preserved across the creation of a process. For example, there are APIs to have a specific thing be fd number 4 so you can run a program and have it find that thing at fd 4. This is weird . Windows, for all its many, many faults, did not use fork+exec and instead mostly has options for how one creates a process. It was…
I just ran into this recently, where I had an obscure bug caused by needing to close more file descriptors in the forked process. "I want a clone of the current process" is just way less common in my experience than "I want a completely new process". It feels crazy that we don't have a way to directly express the latter thing, and can only approximate it by cloning and then fixing things up in post.
But you generally want to communicate with that process, so you do need to setup e.g. file descriptors and stuff, which needs information from the parent process to be passed.
> fork() is a relatively expensive system call; it must copy the entire process state (including memory) for the child process. Many optimizations have been made over the years, but a fork is still a fundamentally costly operation. To make things worse, a fork() call is often immediately followed by an exec(), which will discard all of that memory that was so carefully copied for the child. It's weird to leave out a…
> fork() is a relatively expensive system call; it must copy the entire process state (including memory) for the child process. Many optimizations have been made over the years, but a fork is still a fundamentally costly operation. To make things worse, a fork() call is often immediately followed by an exec(), which will discard all of that memory that was so carefully copied for the child. It's weird to leave out a…
That means you have to allocate new pages to hold a copy of all these structures, even if the actual memory pointed by the pages is shared. And walking all those structures to make a copy is still costly.
The elegance of the fork() + exec() model is that every kind of configuration can be done after the fork using all the usual APIs. Every attempt to replace it with a combined call that I have seen so far seemed fundamentally poorer because it needs to add all configuration options as parameters to the call and then do this in away that you can extend it later and does not become a mess.
I have the entirely opposite opinion. IMO a big mistake of the UNIXy model is that so much state is preserved across the creation of a process. For example, there are APIs to have a specific thing be fd number 4 so you can run a program and have it find that thing at fd 4. This is weird . Windows, for all its many, many faults, did not use fork+exec and instead mostly has options for how one creates a process. It was…
If you want to greenfield re-engineer the world with all new system calls and a totally different execution model, feel free to go right ahead.
The elegance of the fork() + exec() model is that every kind of configuration can be done after the fork using all the usual APIs. Every attempt to replace it with a combined call that I have seen so far seemed fundamentally poorer because it needs to add all configuration options as parameters to the call and then do this in away that you can extend it later and does not become a mess.
Earlier quoted context omitted.
I have the entirely opposite opinion. IMO a big mistake of the UNIXy model is that so much state is preserved across the creation of a process. For example, there are APIs to have a specific thing be fd number 4 so you can run a program and have it find that thing at fd 4. This is weird . Windows, for all its many, many faults, did not use fork+exec and instead mostly has options for how one creates a process. It was…
Is it weirder, that you can pass an variable precisely into argument 4? You do need to pass information to a subprocess and there needs to be some agreement on what means what. Sure, maybe you could use names instead of fds, but that sounds needlessly complicated.