Subject: Re: RAW access to files
To: David Laight <>
From: Wojciech Puchar <>
List: tech-kern
Date: 12/12/2001 22:59:18
> The actual problem is persuading the kernel to discard the correct pages
> (ie those you have just used, rather than the working set of your interactive
> session) when doing (say) a large cp.
and to persuade to read/write pages in LARGE chunks.

> I suspect that pages that hold data that was used by an application mmap()
> that has been unmapped should be near the top of the list of pages to reuse.
> (not those mapped by temporary mappings for standard io though, and maybe
> not code).  Certainly if certain flags are set - eg MADV_SEQUENTIAL.
> The other 'trick' is that page aligned write() calls can be done by
> 'stealing' the memory page from the application (and using copy-on-write).
> (anyone want to work out how to push a memory page through a pipe?)
> For large databases, it might be appropriate to define some way of telling
> the system that it has finished with a part of an mmaped file.