Re: How can TUX user module get notified when a page is removed from cache?

On Thu, 28 Mar 2002, Liang Yang wrote:

> We can use path_walk() to query Linux kernel file system whether a
> specific file is in the memory cache or not, but now we want our TUX
> user space module to get notified regularly from Linux kernel when a
> page is removed from memory cache or a page is added to the memory
> cache? The purpose of this is we try to maintain a table in user module
> to record the status of files which are once accessed. It seems we need
> to install a callback function in TUX user module for this event. How
> can we do that?

could you tell us a bit more about why such a callback is needed?

> BTW, which function can we use to get the information of all cached
> files in Linux kernel so that we can know which files are cached
> currently?

it might be possible to just look at whether the dentry is cached or not.  
Ie. call path_walk with the atomic-lookup bit set, and if it returns a
dentry then the file is 'cached'.

but as long as contents go, a file might be not cached or partially cached
or fully cached. There is no easily accessible information about this -
the pagecache is transparent to TUX.

	Ingo