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From:	"Jan Alphenaar" <jan DOT alphenaar AT dotcolour DOT com>
To:	<cygwin AT cygwin DOT com>
Subject:	FW: Cygwin Rsync/SSH performance issue
Date:	Wed, 17 Feb 2010 12:26:45 +0100
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Hi

At first this email was sent to the developers list, but I understood this
list is more appropriate.

Regards,

Jan


-----Oorspronkelijk bericht-----
Van: Jan Alphenaar [mailto:jan DOT alphenaar AT dotcolour DOT com] 
Verzonden: woensdag 17 februari 2010 12:25
Aan: 'cygwin-developers AT cygwin DOT com'
Onderwerp: RE: Cygwin Rsync/SSH performance issue

Hi,

In an attempt to narrow this down a bit I installed a RedHat machine with
openssh-5.3p1 and rsync-3.0.7 (thus without cygwin) and did the same test as
below.

Transferring data, both up and downstream, are not giving me any CPU load.

Although there is a small version difference in the rsync versions, I would
conclude that this is somehow caused by the cygwin layer.

If anybody can have a look at it, I would really appreciate it. If there is
something I can do, please let me know.

Warm regards,

Jan

-----Oorspronkelijk bericht-----
Van: Jan Alphenaar [mailto:jan DOT alphenaar AT dotcolour DOT com] 
Verzonden: dinsdag 16 februari 2010 16:46
Aan: 'cygwin-developers AT cygwin DOT com'
Onderwerp: RE: Cygwin Rsync/SSH performance issue

Hi again,

I did some more testing on this and figured out that rsync/ssh is only
taking the full cpu if the bandwidth allocated to the session exceeds the
true bandwidth available on the link.

For example, if the uplink is 128KB/s and I pass in the --bwlimit=24
parameter the cpu is around 0%. Even --bw-limit=126 does not take 100% cpu,
but --bwlimit=132 does.

Would this be because of packet loss on the link and packets have to be
retransmitted ? I will do a quick test tonight with rsync/ssh between two
linux boxes, see what that gives me.

Regards,

Jan

-----Oorspronkelijk bericht-----
Van: Jan Alphenaar [mailto:jan DOT alphenaar AT dotcolour DOT com] 
Verzonden: dinsdag 16 februari 2010 11:34
Aan: 'cygwin-developers AT cygwin DOT com'
Onderwerp: Cygwin Rsync/SSH performance issue

Hi everybody,
 
I am using rsync/ssh to copy files from my computer to my server and
everything seems to function as expected, except performance.

During a file transfer on my home computer (Intel I7) there is not a
noticeable CPU load. But on other (older) machines the rsync/ssh transfer
consumes all CPU resources on the sending side. I noticed there are other
questions regarding this subject in the archives, but I could not find a
solution for this. Also throttling the bandwidth to a lower value is not
helping to reduce the CPU load.

I am using quite a basic command to sync my files:

        rsync -e ssh * <user>@<server>:/data

The versions of the software I am using are:

Cygwin: 1.7.1-1
ssh: OpenSSH_5.3p1
rsync: 3.0.6
OS: WinXP

Was anybody able to resolve this ?

Any help is greatly appreciated.

Warm regards,

Jan


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