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Date:	Sat, 24 Mar 2018 17:04:00 -0700
From:	L A Walsh <cygwin AT tlinx DOT org>
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To:	cygwin AT cygwin DOT com
CC:	jgeoghegan60 AT gmail DOT com
Subject:	Re: Network Performance?
References:	<a45d39ab-93e1-41d5-22c7-40a61e355fd5 AT gmail DOT com> <5AB5825C DOT 8060309 AT tlinx DOT org>
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L A Walsh wrote:
> Jordan Geoghegan wrote:
>> Has anyone ever successfully transferred 150Mbps or more over the 
>> network using scp/sftp/rsync etc on Cygwin?
> ----
What is more important? testing cygwin's scp/sftp/rsync, 
or using 'ssh'
or running under cygwin, 
or transferring the file to a local backup server from a windows
client as fast as possible?

Some test notes below(been benching my win<->server 
speeds since Win98 days)...



> Using bs=16.0M, count=64, iosize=1.0G
> R:1073741824 bytes (1.0GB) copied, 1.66724 s, 614MB/s
> W:1073741824 bytes (1.0GB) copied, 3.48363 s, 294MB/s
---
Some additional notes..."/h" is my home directory on the
linux server, so 'bin/iotest is a script in my linux home dir.

The speeds / values using 'Bytes', (2**3) use the base2
prefixes for consistency.  To get values in mbits, multiple
by 8.388608.

The above test only tests transfer speed -- not file i/o --
it uses /dev/zero for a source and /dev/null for a target.

To simplify testing, I created devices 'zero' and 'null'
in my home directory:
(on linux):
> ll zero null
crwxrw-rw- 1 1, 3 May 20  2016 null
crw-rw-rw- 1 1, 5 Jun 15  2015 zero
(on cygwin):
/h> ll zero null
-rwxrw-rw- 1 0 May 20  2016 null*
-rw-rw-rw- 1 0 Jun 15  2015 zero

For write, I used cygwin's 'dd' with if=/dev/zero and of=/h/null.
For read, I used if=/h/zero and of=/dev/null.

Flags for reading: iflag=fullblock conv=nocreat
  and for writing: oflag=direct iflag=fullblock conv=nocreat,notrunc

To test the cpu-bounding, I just tried limiting the clock speeds
on the client and server.
Limiting the linux-server's max cpu-speed had
the most affect on performance: 
(limited to 1.6GHz instead of 2.4GHz) (33% limitation)

Using bs=16.0M, count=256, iosize=4.0G (~35% slowdown)
R:4294967296 bytes (4.0GB) copied, 10.4467 s, 392MB/s
W:4294967296 bytes (4.0GB) copied, 21.5026 s, 190MB/s

Limiting the client (cygwin-win7sp1x64): (~7-13% slowdown)
(clock limited to 1.16GHz instead of 3.2)

Using bs=16.0M, count=256, iosize=4.0G
R:4294967296 bytes (4.0GB) copied, 7.14355 s, 573MB/s
W:4294967296 bytes (4.0GB) copied, 15.9781 s, 256MB/s

This would indicate that even in the unencrypted case
network transfer speed is cpu bound (and this is using
Jumbo packets).





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