Re: dentry bloat.

[Andrew Morton]

viro@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx wrote:
>
> On Sat, May 08, 2004 at 03:11:59AM -0700, Andrew Morton wrote:
> > Andrew Morton <akpm@xxxxxxxx> wrote:
> > >
> > > Here be another patch.
> > 
> > 
> > Can't help myself!
> > 
> > 
> > - d_vfs_flags can be removed - just use d_flags.  It looks like someone
> >   added d_vfs_flags with the intent of doing bitops on it, but all
> >   modifications are under dcache_lock.  4 bytes saved.
> 
> Bzzert.  ->d_vfs_flags modifications are under dcache_lock; ->d_flags ones
> are *not* - they are up to whatever filesystem code happens to use them.

yup, I hunted down the rest.

> > - Pack things so that dentry.d_name.len and dentry.d_flags occupy the same
> >   word.  4 bytes saved.
> 
> d_name.len is accessed on very hot paths.  In particular, we are looking
> at it while traversing hash chains and we do that without dcache_lock
> (see callers of ->d_compare()).

That's OK.  The d_move() d_movecount and locking logic takes care of that. 
But the ushorts are a bit dopey - I'll give those 4 bytes back.

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