4 ms·

> Which is irrelevant, because there is barely any functional difference between the two Well it is relevant, it tells that you're not familiar with the subjec

> Which is irrelevant, because there is barely any functional difference between the two Well it is relevant, it tells that you're not familiar with the subject and most likely googled what looked related and found outdated man pages which seemed related. > Wrong, they absolutely do. "Accessing" something doesn't just involve the IO, it also involves the setup I think common sense would disagree, but if that's your line of arguing, sure. > And the argument in that post stands as solid as it was before. `mmap` MAPS memory. This mapping requires an address translation overhead EVERYTIME THE MEMORY IS ACCESSED. This translation doesn't happen in userspace. How deep are you willing to dig your hole there? Two messages ago you were arguing that accessing a shared memory required syscall and thus was slow. Now you've accepted it doesn't require syscall but argue it requires some magical dynamic translation by the kernel? I'm sorry but again that is just wrong. All the kernel does is inject the mappings when setting up TLB/MMU at context switch. The virtual address translation happens without kernel intervention, through the MMU, in _exactly_ the same manner whether this is a named or anonymous memory mapping, whether it is a shared or heap page. In fact the MMU couldn't care less what these addresses are, it has no concept of the meaning of what it translates.

usrbinbash 3y ago
> it tells that you're not familiar with the subject and most likely googled what looked related and found outdated man pages which seemed related. That is an assumption, for which I have yet to see proof :-) > I think common sense would disagree Please, do enlighten me: How do I access SHM without mapping it first, or otherwise setting it up? > Now you've accepted it doesn't require syscall There was nothing to accept. If you actually read my post, you will see that I talked about the issues of IO and setup seperately. And my point stands still solid ;-) SHM requires syscalls not required when directly using shared memory.

usrbinbash 3y ago

> it tells that you're not familiar with the subject and most likely googled what looked related and found outdated man pages which seemed related. That is an assumption, for which I have yet to see proof :-) > I think common sense would disagree Please, do enlighten me: How do I access SHM without mapping it first, or otherwise setting it up? > Now you've accepted it doesn't require syscall There was nothing to accept. If you actually read my post, you will see that I talked about the issues of IO and setup seperately. And my point stands still solid ;-) SHM requires syscalls not required when directly using shared memory.