Re: splice read byte accounting

[Trond Myklebust <trond.myklebust@fys.uio.no>]

On Thu, 2010-01-28 at 10:07 -0500, Chuck Lever wrote: 
> On Jan 27, 2010, at 6:19 PM, Trond Myklebust wrote:
> > On Wed, 2010-01-27 at 17:22 -0500, Chuck Lever wrote:
> >> Hi-
> >>
> >> nfs_file_splice_write() accounts for the bytes in the request in the
> >> "normal bytes written" counter, but nfs_file_splice_read() does not
> >> account for bytes read.
> >>
> >> Should the read path count these as normal bytes as well, or should
> >> the write path not account for these bytes?
> >>
> >
> > nfs_file_splice_read() should probably update NFSIOS_NORMALREADBYTES.
> >
> > That said, why do nfs_file_read(), nfs_file_write() and
> > nfs_file_splice_write() update the stats with the requested number of
> > bytes, irrespective of the number of bytes that were actually
> > read/write?
> 
> We're counting the number of bytes requested by applications.  I'm not  
> sure which is more useful here; number of bytes requested, or number  
> of bytes actually read/written.  For computing ratios of app bytes v.  
> otw bytes, I suppose the latter?
> 

Yes. Most apps will just be inputting the buffer size as the 'number of
bytes requested', which is not really a particularly useful number.