Re: Interprocess shared memory .... but file backed?

Christopher Quinn
2002-03-08T16:06:18Z

Mark Hahn wrote:

>>>well MAP_PRIVATE is "dont share" so not with that 8)
>>>Use MAP_SHARED and you'll get what you want
>>>
>>Certainly true! But MAP_SHARED gives uncontrolled flush of
>>dirty data - so that's out for me. I only want 'privacy' to
>>extend to the right to make changes permanent at my own
>>discretion.
>>
>
> right, and that's not what Unix provides. in particular, mmap
> is a means for apps to be polite, not for them to strongarm
> the kernel. in particular, if you mmap a file, much of the point
> is that the kernel chooses how much of the state is in ram or
> on disk. you can, of course, msync, or even munmap.
>
>
>

Seems a bit restrictive to me. After all Unix is not an
ossified standard! :)
Assuming clone() actually page table shares the vm covered
by a mmap(MAP_PRIVATE) in the way I want, it isn't much to
ask to be more *restrictive* on sharing?

So far, it's looking as if my ideal is unattainable with the
current kernel.
Anyone disagree?

--
rgrds,
Chris Quinn