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Subject: Re: cygrunsrv + sshd + rsync = 20 times too slow -- throttled?
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From: Ken Brown via Cygwin <cygwin@cygwin.com>
Reply-To: Ken Brown <kbrown@cornell.edu>
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On 8/25/2021 2:18 PM, Chris Roehrig wrote:
> On Wed Aug 25 2021, at 10:52 AM, Ken Brown via Cygwin <cygwin@cygwin.com> wrote:
>> A couple years ago I had an idea for changing the pipe implementation to avoid overlapped I/O:
>>
>>   https://cygwin.com/pipermail/cygwin-patches/2019q2/009393.html
>>   https://cygwin.com/pipermail/cygwin-patches/2019q2/009423.html
>>
>> I never followed up on it.  But if you think it might help with this problem, I could dust it off and try to finish it.
>>
>> Ken
> 
> I'm not familiar enough with the innards of rsync, sshd or cygwin to know how this would work.
> Is it possible to have a new CYGWIN environment option to switch the pipe behaviour without requiring changes to the ssh or rsync source code (and without breaking any existing stuff)?

My proposed change would be purely internal to Cygwin.  There should be no 
user-visible change in behavior except, perhaps, improved performance.  (And we 
don't know yet whether there would be improved performance.)  So I don't see a 
need for a new CYGWIN option.

Ken

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