X-Recipient:	archive-cygwin AT delorie DOT com
DKIM-Filter:	OpenDKIM Filter v2.11.0 sourceware.org DFEE1385500D
DKIM-Signature:	v=1; a=rsa-sha256; c=relaxed/relaxed; d=cygwin.com;
	s=default; t=1629890433;
	bh=4kxSw59PbgHse0LoT+mvgzdMSusCB9gwJMyRhVDDThg=;
	h=Date:To:Subject:In-Reply-To:References:List-Id:List-Unsubscribe:
	List-Archive:List-Post:List-Help:List-Subscribe:From:Reply-To:
	From;
	b=BeMU2yRjbVOswykrbEIdVvaywvP2aDQoePgSAmMxpEIyaqFGvwlZCp3SkwuTcaWSc
	vXZxfJmEDq2y/+678PQyoHz0hkNGErRvOIS1qvMKsff3xCztS9ly7au/XUqQyXXl1o
	rp61Xz85Vn4PI5pvbUxCxjZR5oXzRDf/LiwsrfI0=
X-Original-To:	cygwin AT cygwin DOT com
Delivered-To:	cygwin AT cygwin DOT com
DMARC-Filter:	OpenDMARC Filter v1.4.1 sourceware.org B03593858400
DKIM-Filter:	OpenDKIM Filter v2.10.3 conssluserg-02.nifty.com 17PBIjDQ004725
X-Nifty-SrcIP:	[110.4.221.123]
Date:	Wed, 25 Aug 2021 20:18:45 +0900
To:	cygwin AT cygwin DOT com
Subject:	Re: cygrunsrv + sshd + rsync = 20 times too slow -- throttled?
Message-Id:	<20210825201845.07b6400b79dc5558a7761efe@nifty.ne.jp>
In-Reply-To:	<41A583E1-C8E7-42AB-9F24-EEC33A41EC60@house.org>
References:	<41A583E1-C8E7-42AB-9F24-EEC33A41EC60 AT house DOT org>
X-Mailer:	Sylpheed 3.7.0 (GTK+ 2.24.30; i686-pc-mingw32)
Mime-Version:	1.0
X-Spam-Status:	No, score=-4.7 required=5.0 tests=BAYES_00, DKIM_SIGNED,
	DKIM_VALID, DKIM_VALID_AU, DKIM_VALID_EF, NICE_REPLY_A, RCVD_IN_DNSWL_NONE,
	SPF_HELO_NONE, SPF_PASS, TXREP autolearn=ham autolearn_force=no version=3.4.4
X-Spam-Checker-Version:	SpamAssassin 3.4.4 (2020-01-24) on
	server2.sourceware.org
X-BeenThere:	cygwin AT cygwin DOT com
X-Mailman-Version:	2.1.29
List-Id:	General Cygwin discussions and problem reports <cygwin.cygwin.com>
List-Unsubscribe:	<https://cygwin.com/mailman/options/cygwin>,
	<mailto:cygwin-request AT cygwin DOT com?subject=unsubscribe>
List-Archive:	<https://cygwin.com/pipermail/cygwin/>
List-Post:	<mailto:cygwin AT cygwin DOT com>
List-Help:	<mailto:cygwin-request AT cygwin DOT com?subject=help>
List-Subscribe:	<https://cygwin.com/mailman/listinfo/cygwin>,
	<mailto:cygwin-request AT cygwin DOT com?subject=subscribe>
From:	Takashi Yano via Cygwin <cygwin AT cygwin DOT com>
Reply-To:	Takashi Yano <takashi DOT yano AT nifty DOT ne DOT jp>
Errors-To:	cygwin-bounces+archive-cygwin=delorie DOT com AT cygwin DOT com
Sender:	"Cygwin" <cygwin-bounces+archive-cygwin=delorie DOT com AT cygwin DOT com>

On Tue, 24 Aug 2021 12:49:52 -0700
Chris Roehrig wrote:
> I have a network of Windows, Linux and Mac machines and I use rsync to synchronize various directories between them.
> 
> I'm trying to figure out why my rsync transfers are so slow (<4 MB/s) only when the remote endpoint is Cygwin rsync over sshd (with both a Linux or Cygwin rsync client).   In all other scenarios, I get the full 100MB/s as expected from gigabit ethernet.  This has been an ongoing problem for me for a couple of years over several Windows and Cygwin versions, and I'd like to try to fix it.    
> 
> If I run rsync --daemon --no-detach under mintty in the foreground on the remote Windows endpoint,  I get the full 100 MB/s transfers, so it seems like it has something to do with rsync.exe running in the background under the cygrunsrv+sshd service (which was installed normally using ssh-host-config).
> 
> If I do:
> 	pv /dev/zero | ssh $WINHOST "cat > /dev/null"
> or even
> 	pv /dev/urandom | ssh $WINHOST md5sum
> I also get the full 100 MB/s transfers, so it doesn't look like sshd itself is being throttled by bandwidth or CPU.
> 
> The machines have less than 15% CPU utilization while transferring, with each of the 4 cores less than 30%, so it doesn't look to be CPU issue.
> In Task Manager, sshd.exe and rsync.exe seem to be running normally using only few percent CPU, and show Power Throttling=Disabled, Priority=Normal.   Setting their Priority to High doesn't seem to change things.
> 
> Looking in Resource Monitor on the remote endpoint, the network usage is pretty much a flat horizontal line at about 18 Mbps (2.5 MB/s), so it sure looks to me as if rsync is somehow being bandwidth-throttled when run in the background under cygsshd.
> 
> It's almost as if rsync has an implicit --bwlimit override when it is run from cygrunsrv+sshd (I've tried --bwlimit=0 on the client which makes no difference).
> 
> 
> Any ideas?    Not sure where to go from here. 

In cygwin, just scp is very slow.

The transfer speed in my environment is as follows.
The tests were done with 100MB of test.dat file.

(1-1) From cygwin-PC,
[yano AT cygwin-PC ~]$ scp test.dat yano AT linux-server:.
yano AT linux-server's password:
test.dat                                      100%  100MB   4.0MB/s   00:24
[yano AT cygwin-PC ~]$ scp yano AT linux-server:test.dat .
yano AT linux-server's password:
test.dat                                      100%  100MB   8.0MB/s   00:12

(1-2) From linux-server,
yano AT linux-server:~$ scp yano AT cygwin-PC:test.dat .
yano AT cygwin-PC's password:
test.dat                                      100%  100MB   4.0MB/s   00:24
yano AT linux-server:~$ scp test.dat yano AT cygwin-PC:.
yano AT cygwin-PC's password:
test.dat                                      100%  100MB   4.1MB/s   00:24


I looked into this problem, and noticed that this is caused
by cygwin pipe implementation. Pipe in cygwin is configured
with FILE_FLAG_OVERLAPPED.

If the pipe is configured without FILE_FLAG_OVERLAPPED,
the transfer speed is much improved as follows.


(2-1) From cygwin-PC,
[yano AT cygwin-PC ~]$ scp test.dat yano AT linux-server:.
yano AT linux-server's password:
test.dat                                      100%  100MB  85.5MB/s   00:01
[yano AT cygwin-PC ~]$ scp yano AT linux-server:test.dat .
yano AT linux-server's password:
test.dat                                      100%  100MB  69.7MB/s   00:01

(2-2) From linux-server,
yano AT linux-server:~$ scp yano AT cygwin-PC:test.dat .
yano AT cygwin-PC's password:
test.dat                                      100%  100MB  80.1MB/s   00:01
yano AT linux-server:~$ scp test.dat yano AT cygwin-PC:.
yano AT cygwin-PC's password:
test.dat                                      100%  100MB  57.7MB/s   00:01

I am not sure why this happens and how to fix this.
Any idea?

-- 
Takashi Yano <takashi DOT yano AT nifty DOT ne DOT jp>

-- 
Problem reports:      https://cygwin.com/problems.html
FAQ:                  https://cygwin.com/faq/
Documentation:        https://cygwin.com/docs.html
Unsubscribe info:     https://cygwin.com/ml/#unsubscribe-simple

- Raw text -