Re: [boost] [interprocess] shared memory lifetime

From: Olaf van der Spek (olafvdspek_at_[hidden])
Date: 2006-03-10 18:15:21

On 3/10/06, Kim Barrett <kab_at_[hidden]> wrote:
> >One option is to use a memory mapped file to emulate posix-like behavior
> >in windows. But it surely will be slower (the OS will dump data to file)
> >and the unlink is not trivial.
>
> That does seem like it would be bad if true. Are there any file
> manipulation options that might be used to control that? I don't know,
> but I'll ask around and do some reading and see what I can find.
>
> [Later] As long as you don't flush the file it would seem like a memory
> mapped file should be no different from a shared memory in performance,
> the only difference is where data gets written if it needs to be swapped
> out. The big downside to using an actual file would be that you need a
> place in the file system to put it. Then you get into the whole name of
> the shared memory portability problem again.

The OS will probably write dirty pages to disk even before paging them
out so that if it needs to page them out it doesn't have to also do a
disk write.