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

[Corinna Vinschen]

On Aug 31 18:25, Takashi Yano wrote:
> On Tue, 31 Aug 2021 11:08:42 +0200
> Corinna Vinschenwrote:
> > On Aug 31 17:55, Takashi Yano wrote:
> > > On Mon, 30 Aug 2021 22:14:15 +0200
> > > Corinna Vinschen wrote:
> > > > Hi Ken, Hi Takashi,
> > > > 
> > > > On Aug 30 19:00, Corinna Vinschen wrote:
> > > > Well, what about keeping a duplicate of the read side handle on the 
> > > > write side just for calling NtQueryInformationFile?
> > > > 
> > > > Attached is an untested patch, can you have a look if that makes sense?
> > > > 
> > > > Btw., I think I found a bug in the new fhandler_pipe::create.  If the
> > > > function fails to create the write side fhandler, it deletes the read
> > > > side fhandler, but neglects to close the read handle.  My patch fixes
> > > > that.
> > > > 
> > > > While looking into this I found a problem in fhandler_disk_file in
> > > > terms of handle inheritance of the special handle for pread/pwrite.
> > > > I already force pushed this onto topic/pipe.
> > > 
> > > I tested your patch attached. Unfortunately, select() does not work
> > > as expected for write pipe. Even if the select reports write pipe
> > > is available, writing to pipe fails. It seems that your patch fails
> > > to detect pipe full.
> > 
> > Bummer.  Is that with byte mode pipes or with message mode pipes?  If
> > the latter, if you try to write more data than available in the buffer,
> > it's bound to fail.
> 
> Both message pipe and byte pipe.
> 
> > Did you add debug output to pipe_data_available to see how the
> > information looks like?  Or do you have a simple, self-contained
> > testcase in plain C?
> 
> The test case is attached. If select() works as expected, the program
> does not show "r" or "w". However, with your patch, the program prints
> many "w" (means write() fails with EAGAIN).

Thanks!  I found th culprit, but we have another problem.  Even if
select returns correct info,  A write, trying to write more bytes
than are available in the buffer, hangs.  This shouldn't happen.
Still digging...


Corinna