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

[Corinna Vinschen]

On Aug 30 21:04, Takashi Yano wrote:
> On Mon, 30 Aug 2021 12:20:30 +0200
> Corinna Vinschen wrote:
> > [Move discussion to cygwin-developers]
> > 
> > On Aug 30 17:02, Takashi Yano via Cygwin wrote:
> > > [...]
> > > Is naming the pipe really necessary?
> > 
> > It's not, but CreatePipe is doing this anyway.
> > 
> > "Anonymous pipes are implemented using a named pipe with a unique name."
> > https://docs.microsoft.com/en-us/windows/win32/api/namedpipeapi/nf-namedpipeapi-createpipe
> > 
> > The reason CreateNamedPipe was used in the first place was that
> > FILE_READ_ATTRIBUTES isn't set by CreatePipe for the write side
> > of the pipe, however, it creates full duplex pipe:
> > 
> > https://cygwin.com/pipermail/cygwin-patches/2004q3/004912.html
> > 
> > Given the fact that CreatePipe is implemented in terms of
> > NtCreateNamedPipeFile anyway, why should the pipe created with
> > NtCreateNamedPipeFile fail where the pipe created with CreatePipe works?
> > 
> > The only reason can be some missing flag, I think.  Checking
> > fhandler_pipe.cc::nt_create and comparing that with the default flags
> > for files and other devices, it occurs to me that the SYNCHRONIZE stuff
> > is missing.  So, Takashi, what if you call NtCreateNamedPipeFile like
> > this in nt_create:
> > 
> >   status = NtCreateNamedPipeFile (r, access | SYNCHRONIZE, &attr, &io,
> > 				  FILE_SHARE_READ | FILE_SHARE_WRITE,
> > 				  FILE_CREATE, FILE_SYNCHRONOUS_IO_NONALERT,
> > 				  pipe_type, FILE_PIPE_BYTE_STREAM_MODE,
> > 				  0, 1, psize, psize, &timeout);
> > 
> > Does that fix the above problems, too?
> 
> Yes it does! Now, if CYGWIN=pipe_byte is also set, the piping issue
> of C# program is gone!
> 
> In fact, I've already tested adding the SYNCHRONIZE access flag,
> but it didn't solve the problem. It seems that the cause was
> that FILE_SYNCHRONOUS_IO_NONALERT was missing.
> 
> Thank you for figuring out the solution!

No worries.  The same should apply to the NtCreateFile side of the
pipe, btw.


Corinna