Rsync performance increase through buffering

[Dave Dykstra]

Craig, I'd like to get your patch into the 2.5.6 patches directory.
Could you please make sure it applies cleanly onto version 2.5.6pre1 (see
news on http://rsync.samba.org home page if you haven't been following
the mailing list) and repost it?

Thanks,

- Dave Dykstra

On Wed, Dec 11, 2002 at 03:20:57PM -0600, Dave Dykstra wrote:
> On Sun, Dec 08, 2002 at 11:48:57PM -0800, Craig Barratt wrote:
> > I've been studying the read and write buffering in rsync and it turns
> > out most I/O is done just a couple of bytes at a time.  This means there
> > are lots of system calls, and also most network traffic comprises lots
> > of small packets.  The behavior is most extreme when sending/receiving
> > file deltas of identical files.
> ...
> > Below is a patch to a few files that adds read and write buffering in
> > the places where the I/O was unbuffered, adds buffering to write_file()
> > and removes the unneeded gettimeofday() system call in show_progress().
> ...
> > However, on a network test doing a send from cygwin/WinXP to rsyncd
> > on rh-linux the running time improves from about 700 seconds to 215
> > seconds (with a cpu load of around 17% versus 58%, if you believe
> > cygwin's cpu stats).  This is probably an extreme case since the system
> > call penalty in cygwin is high.  But I would suspect a significant
> > improvement is possible with a slow network connection, since a lot
> > less data is being sent.
> 
> Looks like a good candidate for the "patches" directory now and for
> integration in 2.6.0.
> 
> - Dave