Mail Archives: cygwin/2021/08/26/11:56:51

Ken Brown via Cygwin <cygwin AT cygwin DOT com> · Thu, 26 Aug 2021 11:56:07 -0400

On 8/25/2021 5:29 PM, Takashi Yano wrote:
> On Wed, 25 Aug 2021 13:52:19 -0400
> Ken Brown wrote:
>> On 8/25/2021 7:18 AM, Takashi Yano via Cygwin wrote:
>>> 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.
>>
>> A couple years ago I had an idea for changing the pipe implementation to avoid
>> overlapped I/O:
>>
>>     https://cygwin.com/pipermail/cygwin-patches/2019q2/009393.html
>>     https://cygwin.com/pipermail/cygwin-patches/2019q2/009423.html
>>
>> I never followed up on it.  But if you think it might help with this problem, I
>> could dust it off and try to finish it.
> 
> Interesting.
> 
> It will be also helpfull for:
> https://cygwin.com/pipermail/cygwin/2021-March/247987.html
> which seems to be the same issue with
> https://stackoverflow.com/questions/10385424/good-alternatives-to-cygwin-cygwin-doesnt-support-natively-support-win32-app
> 
> However, I wonder why scp dislikes overlapped I/O.

I agree that it would be good to understand this.  When I first proposed the 
change, I was thinking in terms of code simplification.  If it also improves 
performance (which we don't know yet), it becomes a higher priority, but in that 
case it would be nice to understand why it improves performance.

Ken

-- 
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

X-Recipient:	archive-cygwin AT delorie DOT com
DKIM-Filter:	OpenDKIM Filter v2.11.0 sourceware.org 62B4D3858039
DKIM-Signature:	v=1; a=rsa-sha256; c=relaxed/relaxed; d=cygwin.com;
	s=default; t=1629993410;
	bh=BozF0XHn2EgUxh1KPK3tlfGwNZmd6OZyu+3fIKxnWVo=;
	h=Subject:To:References:Date:In-Reply-To:List-Id:List-Unsubscribe:
	List-Archive:List-Post:List-Help:List-Subscribe:From:Reply-To:
	From;
	b=saof8pLhqpizk3ZnE2CyPK3vh/n83p3psIhoQ9bvl5mjPOlUVLp6zZi98CTzvV/7x
	WAhbLyakPalPTdJn8DEGOSJueUs+K/qzdMZx6Mwcmz4EeUuUGYOcNMaE59gka6nNXy
	0j3XZc8pgmLij4EkunMgNHR+BtyjhfRkwEkLb1Zc=
X-Original-To:	cygwin AT cygwin DOT com
Delivered-To:	cygwin AT cygwin DOT com
DMARC-Filter:	OpenDMARC Filter v1.4.1 sourceware.org 26F683858D3C
ARC-Seal:	i=1; a=rsa-sha256; s=arcselector9901; d=microsoft.com; cv=none;
	b=HLcr4TSaN5aE00/iYIW69IowMxlyCZOIlhAYenhi8XDB8CROzVFz+pBes5gqpaeFVjsxrtja9bIhotMzJQUWQ9CdETCTLWFwPZzIBA8L6kqJrdF/fbGKMp9a0pOQODXRSP6RwOpjcFOoGttAY+3xrqW9za3gIZgOzryOwm44C9lSU82Lac+bShlOtxOXHqbELFvdRwcaLV0c5wjfs/PAS4ylxz8lXz69w+K/dR+OqjcZff6OPQ57mxGhJkAabnlF1PjBo13Yy5gOvBDHC0GwtzEnlUsGjOeO6ZOcuCbBZXlAGePzlX/s5V7lRFSRk3KQjfX+Sk8+JJpOXOHXZaiK/A==
ARC-Message-Signature:	i=1; a=rsa-sha256; c=relaxed/relaxed; d=microsoft.com;
	s=arcselector9901;
	h=From:Date:Subject:Message-ID:Content-Type:MIME-Version:X-MS-Exchange-SenderADCheck;
	bh=j9nMTQf6UA8g3fai0Ysks0W4w3akjEoKeSkQ0eGILqk=;
	b=QdrQR4UfoTFxzvLRtcDQXh0BUe4oGP1XcneIQrzTheOcvCwknubkoWxeXCUo0wXXM1F4oL0uCtY0CbAvPhWJCuNtd1Ups2/JZJJw0i4qr/xcH5Nh8KLT+vrMTcaXjH5HXrCa0ZHGWsaPLq8GiA4e4UUn3gnIwBgyKfD8tceiFiWv6w85B2w3fkCxtvk0Kdyfkpry2AeBb1eJ7KznZAzQYV5ZhpT8kudd2LOpKFSK0cTY8C6Q5VujJR62ezZYF9HIqJ7g71GLsPsX7rDXmg/jFCGmJ57QYns77WiYSgO8yfHbUoi683dqPgLpwqtvnuVf5l+0IWsEg+CBd/qZkJYTEA==
ARC-Authentication-Results:	i=1; mx.microsoft.com 1; spf=pass
	smtp.mailfrom=cornell.edu; dmarc=pass action=none header.from=cornell.edu;
	dkim=pass header.d=cornell.edu; arc=none
Subject:	Re: cygrunsrv + sshd + rsync = 20 times too slow -- throttled?
To:	cygwin AT cygwin DOT com
References:	<41A583E1-C8E7-42AB-9F24-EEC33A41EC60 AT house DOT org>
	<20210825201845 DOT 07b6400b79dc5558a7761efe AT nifty DOT ne DOT jp>
	<f8106fe7-a2b8-d106-3061-4d888124f4b0 AT cornell DOT edu>
	<20210826062934 DOT 54f2f2216021c095bb7ba13b AT nifty DOT ne DOT jp>
Message-ID:	<d0a8c57d-1ed1-6b4f-c6e7-cbe0e2ec8a1c@cornell.edu>
Date:	Thu, 26 Aug 2021 11:56:07 -0400
User-Agent:	Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:78.0) Gecko/20100101
	Thunderbird/78.13.0
In-Reply-To:	<20210826062934.54f2f2216021c095bb7ba13b@nifty.ne.jp>
X-ClientProxiedBy:	CH2PR07CA0055.namprd07.prod.outlook.com
	(2603:10b6:610:5b::29) To BN7PR04MB4388.namprd04.prod.outlook.com
	(2603:10b6:406:f8::19)
MIME-Version:	1.0
X-MS-Exchange-MessageSentRepresentingType:	1
X-MS-PublicTrafficType:	Email
X-MS-Office365-Filtering-Correlation-Id:	0a15499c-7ca7-4aca-1442-08d968aa0502
X-MS-TrafficTypeDiagnostic:	BN6PR04MB0899:
X-Microsoft-Antispam-PRVS:	<BN6PR04MB089949D13D694D0A1747322AD8C79 AT BN6PR04MB0899 DOT namprd04 DOT prod DOT outlook DOT com>
X-MS-Oob-TLC-OOBClassifiers:	OLM:3968;
X-MS-Exchange-SenderADCheck:	1
X-MS-Exchange-AntiSpam-Relay:	0
X-Microsoft-Antispam:	BCL:0;
X-Microsoft-Antispam-Message-Info:	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
X-Forefront-Antispam-Report:	CIP:255.255.255.255; CTRY:; LANG:en; SCL:1; SRV:;
	IPV:NLI; SFV:NSPM; H:BN7PR04MB4388.namprd04.prod.outlook.com; PTR:; CAT:NONE;
	SFS:(4636009)(396003)(136003)(346002)(366004)(376002)(39860400002)(66946007)(8936002)(186003)(478600001)(75432002)(6916009)(66556008)(2616005)(66476007)(6486002)(36756003)(31686004)(83380400001)(31696002)(316002)(38100700002)(966005)(786003)(53546011)(8676002)(86362001)(2906002)(5660300002)(45980500001)(43740500002)(460985005);
	DIR:OUT; SFP:1102;
X-MS-Exchange-AntiSpam-MessageData-ChunkCount:	1
X-MS-Exchange-AntiSpam-MessageData-0:	=?Windows-1252?Q?sNJ8zvEqY+MzxQBXnr2nS4piH7P2v09HVrBSAYP2whWF7cq7p4B5S6dp?=
	=?Windows-1252?Q?5kth+67kzuBlSb313zMI0qtyyKwWPzoAznjqZgH4eR6vHIHDuc8PFZEt?=
	=?Windows-1252?Q?sr8KqTN/XjVmgyHNYXKVri/2ChVahf8WyQxPSLv8odTijTsAMksIt8ka?=
	=?Windows-1252?Q?+27x44R6B33c8Qc+onu/5x1fF6XrXWAs2YZf++VhwxWMCYKUUixxVv1/?=
	=?Windows-1252?Q?gTlOgs6e7235cSy+B+HsMa60HTanx2QjbAnzbOeDrQ48pAf/dTobpgW2?=
	=?Windows-1252?Q?D5Kxm+4x1lsY0WnXcl+yHZuXUSP1PC7+GCT6PFj+4zKfjw0aasO9m6L+?=
	=?Windows-1252?Q?KkKpmdCWXIfqTXZfwXia4NGxcacKMCpgDUO7HQVjY2rQQGaBTeOxGFeP?=
	=?Windows-1252?Q?V++dtNVeGb4ZNVtk/kvVyPVJt0reKRmXF99gfLDnDRBDI14eBwQN36W3?=
	=?Windows-1252?Q?c7nZiuFE9XKGk+5WlFtHrXPrGADOEsDTTdU+8vhphWlXwfhX5W5148rL?=
	=?Windows-1252?Q?wE1+aHkmztbsIAjhPtzzL4wusHmS4pEEVK5LM0Ve0wBLRSZ7XLsF5Ryt?=
	=?Windows-1252?Q?FzwY+mI6/q57Q8RzT07Tx3U88N51PQSQ4rf6K8yzm0HcAVY/bXK3J4I2?=
	=?Windows-1252?Q?dt3I1Zv0A3rE6dFNocKt6lJRXKXHGbHwz2sRufuAD7du/YSu66xiKPYW?=
	=?Windows-1252?Q?Np3bh/p67L2RggXy9+Xcnd8cIAxySr6PNjdefXz2sw9CEC7gEN8rDLlG?=
	=?Windows-1252?Q?hcQa2UKBTGjs+fyxJicxj9K6hrRm9/2asxx7nT+KsQrDtjZ4xT8ZluX3?=
	=?Windows-1252?Q?XB4ZFqBnyO9A2+kt3WXMRmfBQ+jdveXJ+fQ5Lq5gNCPGk3Qxf7jEyy9r?=
	=?Windows-1252?Q?yiv1Zwq3L9Ds8z4pW55zh8Y1YAwNSKWbGeW/Vz98aErGZwhwDxpPBgwd?=
	=?Windows-1252?Q?sHafLSqvJVChDBOy5NgiBzjtYalu7aK7EvwJ3K6Oeh8eoO6DbONjG0My?=
	=?Windows-1252?Q?F7TQuLkiYN2VfeOQDFs8gF3LO8n+CjOXPnulHF7M5TomlHrsLAEJCmRd?=
	=?Windows-1252?Q?yLTYla9TGZydhlqso6uVyfnofevfm1CQd4Rd56XfHU7SHtTGD6gsmlgP?=
	=?Windows-1252?Q?r6NA1DoyDiiQP0bISNk32vuKa1qXT3sH/7NGuWlXGp6fH5FH+WpWQKaG?=
	=?Windows-1252?Q?ca3+qp+TTHxvDD9rChT62Nwl02IVwhbVZ0hb3psAEjBXqLdSEkHbRN1T?=
	=?Windows-1252?Q?BlLcwND3POowdTMPzAn4lBKGqIXQjEaE+bgk9VdvZ/4Wt5V2yLSWo3Dr?=
	=?Windows-1252?Q?HrY5ZFhxxnoShiM0OFMEfvZ8fyh8YzYP3R4g5nnv3tf9OjZzm7tAKu0q?=
	=?Windows-1252?Q?Hcn+BgLfqCFLLG757mpDA8TbIVwGGx8tqH2Oni3jWA3SwaL+Kqo1DP/l?=
	=?Windows-1252?Q?pTYwcDs1+ZaTcwfmzwHr5tfR0BJb5isMaP75gg5hCluRwolZh/AStKX9?=
	=?Windows-1252?Q?1uIysW+m?=
X-OriginatorOrg:	cornell.edu
X-MS-Exchange-CrossTenant-Network-Message-Id:	0a15499c-7ca7-4aca-1442-08d968aa0502
X-MS-Exchange-CrossTenant-AuthSource:	BN7PR04MB4388.namprd04.prod.outlook.com
X-MS-Exchange-CrossTenant-AuthAs:	Internal
X-MS-Exchange-CrossTenant-OriginalArrivalTime:	26 Aug 2021 15:56:08.9006 (UTC)
X-MS-Exchange-CrossTenant-FromEntityHeader:	Hosted
X-MS-Exchange-CrossTenant-Id:	5d7e4366-1b9b-45cf-8e79-b14b27df46e1
X-MS-Exchange-CrossTenant-MailboxType:	HOSTED
X-MS-Exchange-CrossTenant-UserPrincipalName:	SAlIfgwFKvkLwVhICBiG5xrO7ewZ4W1ic5yJLWdkrFUaNlp6DiewC9zp3uupnc+8VBW+QDM/EEvyrpopTf9qkg==
X-MS-Exchange-Transport-CrossTenantHeadersStamped:	BN6PR04MB0899
X-Spam-Status:	No, score=-4.2 required=5.0 tests=BAYES_00, DKIM_SIGNED,
	DKIM_VALID, DKIM_VALID_AU, DKIM_VALID_EF, MSGID_FROM_MTA_HEADER, NICE_REPLY_A,
	RCVD_IN_DNSWL_NONE, RCVD_IN_MSPIKE_H2, SPF_PASS, TXREP,
	T_SPF_HELO_TEMPERROR 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:	Ken Brown via Cygwin <cygwin AT cygwin DOT com>
Reply-To:	Ken Brown <kbrown AT cornell DOT edu>
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>

webmaster	delorie software privacy
Copyright � 2019 by DJ Delorie	Updated Jul 2019