Re: New nanosecond stat patch for 2.5.44

[Jamie Lokier <lk@tantalophile.demon.co.uk>]

Bill Davidsen wrote:
> > Oh, the inode of a file which is open does remain in core.  It's just
> > that between runs of a program like "make", the file's aren't open are
> > they?
> 
> I thought we were talking about parallel make, rather than "between runs."

A parallel build often does call "make" separately many times, in
parallel but not guaranteed to overlap all file opens.  Between those,
the files are closed.

> Your point is valid, but given the certainty that the inode has been
> recently used, hopefully the kernel is smart on releasing them.

That's a "hopefully", and it depends on how much RAM you have as well
as pure luck.  I can live with that for building programs at home, but
there are many applications where "hopefully" affecting correctness of
behaviour is not acceptable.

> My first thought is that the commonly used filesystems, other than ext2,
> do or will support high resolution time. NFS is its own nasty little
> problem.

Do they support nanosecond time, though, or do they round it to
microseconds or something like that?

> [stuff about atime]

There seems to be general agreement that atime is not a very important
value, with which I concur.  (Why do we even bother with nanosecond atimes?)

I am only concerned about mtime, which is very useful indeed when we
talk about building things which can detect changes to files.

Andi, I belive there is space in every architecture's stat64 (i.e. all
those that have one) for a word describing the mtime resolution.  If I
code a patch to create that field, would you be interested?

-- Jamie