[Ocfs2-devel] [PATCH] Reoganize data elements to reduce memory footprint

[Joel Becker]

On Wed, Jun 09, 2010 at 05:45:10PM -0700, Joel Becker wrote:
> On Wed, Jun 09, 2010 at 04:57:11PM -0500, Goldwyn Rodrigues wrote:
> > diff --git a/fs/ocfs2/ocfs2.h b/fs/ocfs2/ocfs2.h
> > index c67003b..34b9c79 100644
> > --- a/fs/ocfs2/ocfs2.h
> > +++ b/fs/ocfs2/ocfs2.h
> > @@ -151,17 +151,16 @@ struct ocfs2_lock_res {
> >  	void                    *l_priv;
> >  	struct ocfs2_lock_res_ops *l_ops;
> >  	spinlock_t               l_lock;
> > +	enum ocfs2_lock_type     l_type;
> 
> 	I think you should change l_type, l_action, l_requested,
> l_blocking, and l_level to unsigned char.  While the enums that set them
> should be not modified, they do not have more than 256 values.  All the
> functions around them can use the enum type in their arguments.  Just
> the ocfs2_lock_res itself stores them in unsigned char.
> 	This would potentially save us 15 bytes per ocfs2_lock_res,
> 45 per inode.  More realistic is probably 12 per lock_res and 36 per
> inode, but still!

	If you do this, please comment that they are set from enums but
are unsigned char to save space because the value never overflows.

Joel

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Joel Becker
Principal Software Developer
Oracle
E-mail: joel.becker at oracle.com
Phone: (650) 506-8127