cygrunsrv + sshd + rsync = 20 times too slow -- throttled?

[Ken Brown]

On 8/27/2021 7:24 AM, Takashi Yano wrote:
> On Thu, 26 Aug 2021 18:18:29 -0400
> Ken Brown wrote:
>> On 8/26/2021 11:56 AM, Ken Brown via Cygwin wrote:
[...]
>> In case you want to try out my proposed change, I've just rebased the patches to
>> the current master and pushed them to a new topic/pipe branch.
> 
> Hi Ken,
> 
> Thanks much! I tested topic/pipe branch.
> 
> [yano@cygwin-PC ~]$ scp test.dat yano@linux-server:.
> yano@linux-server's password:
> test.dat                                      100%  100MB  95.9MB/s   00:01
> [yano@cygwin-PC ~]$ scp yano@linux-server:test.dat .
> yano@linux-server's password:
> test.dat                                      100%  100MB   8.0MB/s   00:12
> 
> yano@linux-server:~$ scp yano@cygwin-PC:test.dat .
> yano@cygwin-PC's password:
> test.dat                                      100%  100MB 109.7MB/s   00:00
> yano@linux-server:~$ scp test.dat yano@cygwin-PC:.
> yano@cygwin-PC's password:
> test.dat                                      100%  100MB  31.4MB/s   00:03
> 
> As shown above, outgoing transfer-rate has been improved upto near
> theoretical limit. However, incoming transfer-rate is not improved
> much.
> 
> I digged further and found the first patch attached solves the issue
> as follows.
> 
> [yano@cygwin-PC ~]$ scp yano@linux-server:test.dat .
> yano@linux-server's password:
> test.dat                                      100%  100MB 112.8MB/s   00:00
> 
> yano@linux-server2:~$ scp test.dat yano@cygwin-PC:.
> yano@cygwin-PC's password:
> test.dat                                      100%  100MB 102.5MB/s   00:00

Great!

> I also tested the case:
>>>> 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
> 
> Unfortunately, topic/pipe does not help.
> 
> I confirmed that applying the second patch attached, which reverts
> to create() rather than nt_create(), and setting CYGWIN=pipe_byte
> fixes the problem.
> 
> What do you think of this alternative implementation which does
> not use nt_create()?

Two years ago I thought I needed nt_create to avoid problems when calling 
set_pipe_non_blocking.  Are you saying that's not an issue?  Is 
set_pipe_non_blocking unnecessary?  Is that the point of your modification to 
raw_read?

Ken