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

[Corinna Vinschen <corinna-cygwin@cygwin.com>]

On Aug 31 17:18, Corinna Vinschen wrote:
> On Aug 31 08:33, Ken Brown wrote:
> > On 8/31/2021 7:45 AM, Takashi Yano wrote:
> > > On Tue, 31 Aug 2021 12:18:57 +0200
> > > Corinna Vinschen wrote:
> > > > Please try the attached patch on top of topic/pipe.
> > > 
> > > Thanks for the new patch. I have confirmed that above issue
> > > is fixed and select() for write pipe seems to work as expected.
> > > 
> > > 
> > > BTW, I found one minor difference between Linux and this pipe
> > > implementation.
> > > [...]
> > > Is this difficult to be fixed?
> > Two other remarks:
> > 
> > 1. I think query_hdl needs to be initialized in the fhandler_pipe constructor.
> 
> No, that's not necessary.  The fhandlers are always ccalloc'ed so they
> are all 0 anyway.
> 
> > 2. When the read side of the pipe is non-blocking, there can be no pending
> > reads, so shouldn't we be able to use WriteQuotaAvailable reliably on the
> > write side?  (I can't test this at the moment.)
> 
> In theory, yes, but is it a safe bet that non-blocking reads won't change
> WriteQuotaAvailable on the write side, at least for a very short time?
> The question is, of course, if that really makes much of a difference.

Oh, btw... why do you want to use WriteQuotaAvailable for normal
pipes, even though the read side information is available anyway?

We can do that for fifos, no problem, but it doesn't make much sense
to differ between blocking and non-blocking pipes, the code flow is the
same.


Corinna