Re: Questions about the buffer+page cache in 2.4.0

[Andi Kleen]

On Sat, Jul 29, 2000 at 06:58:34PM +0200, Gary Funck wrote:
> What entity is responsible for tearing down the file<->page mapping, when
> the storage is needed?  Is that bdflush's job?

kswapd's and the allocators themselves.

> 
> In 2.4, does the 'read actor' (ie, for ext2) optimize the case where
> the part of the I/O request being handled has a user-level address that
> is page aligned, and the requested bytes to transfer are at least one
> full page?  Ie, does it handle the 'copy' by simply remapping the I/O
> page directly into the user's address space (avoiding a copy)?

No, because you cannot avoid the copy anyways because you need to maintain
cache coherency in the page cache. If you want zero copy IO use mmap().


-Andi