X-Recipient: archive-cygwin AT delorie DOT com X-Original-To: cygwin AT cygwin DOT com Delivered-To: cygwin AT cygwin DOT com DMARC-Filter: OpenDMARC Filter v1.4.1 sourceware.org 4260A3857C67 Authentication-Results: sourceware.org; dmarc=none (p=none dis=none) header.from=house.org Authentication-Results: sourceware.org; spf=pass smtp.mailfrom=house.org X-Virus-Scanned: Debian amavisd-new at emo01-pco.easydns.vpn Mime-Version: 1.0 (Mac OS X Mail 6.2 \(1499\)) Subject: Re: cygrunsrv + sshd + rsync = 20 times too slow -- throttled? From: Chris Roehrig In-Reply-To: Date: Wed, 25 Aug 2021 11:18:14 -0700 Message-Id: References: <41A583E1-C8E7-42AB-9F24-EEC33A41EC60 AT house DOT org> <20210825201845 DOT 07b6400b79dc5558a7761efe AT nifty DOT ne DOT jp> To: "cygwin AT cygwin DOT com" X-Mailer: Apple Mail (2.1499) X-Spam-Status: No, score=-1.9 required=5.0 tests=BAYES_00, KAM_DMARC_STATUS, 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 Precedence: list List-Id: General Cygwin discussions and problem reports List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Errors-To: cygwin-bounces+archive-cygwin=delorie DOT com AT cygwin DOT com Sender: "Cygwin" On Wed Aug 25 2021, at 10:52 AM, Ken Brown via Cygwin wrote: > 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. > > Ken I'm not familiar enough with the innards of rsync, sshd or cygwin to know how this would work. Is it possible to have a new CYGWIN environment option to switch the pipe behaviour without requiring changes to the ssh or rsync source code (and without breaking any existing stuff)? - Chris > 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. > > > > -- > 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 -- 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