Re: [PATCH v2] Sleep 1 millisecond in poll() to avoid busy wait

> Hello Junio,
>
> thank you for pointing out the problems.
>
> Let me explain the background:
>
> After some discussion a one line fix to win32/poll.c was accepted to msysgit/git
> at 2012-05-16 https://github.com/msysgit/git/pull/7
>
> The description of the commit looked like this:
>> I played around with this [...]
>> [...]
>> I also tested the very fast local case, and didn't see any measurable
>> difference. On a big repo with 4500 files, the upload-pack took about 2
>> seconds with and without the fix.
> ... but there was no sign-off by Theodore.
>
> Because poll.c comes from Gnulib, it was reported there as well.
> Paolo Bonzini accepted the fix for poll.c and added a fix for select.
> The combined commit got this changelog entry:
>
>> 2012-05-21  Paolo Bonzini  <bonzini@gnu.org>
>> 
>>         poll/select: prevent busy-waiting.  SwitchToThread() only gives away
>>         the rest of the current time slice to another thread in the current
>>         process. So if the thread that feeds the file decscriptor we're
>>         polling is not in the current process, we get busy-waiting.
>>         * lib/poll.c: Use SleepEx(1, TRUE) instead of SwitchToThread().
>>         Patch from Theodore Leblond.
>>         * lib/select.c: Split polling out of the loop that sets the output
>>         fd_sets.  Check for zero result and loop if the wait timeout is
>>         infinite.
>
> The patch that I (Stepan) submitted as "v2" combines things like this:
> - subject by Theodore
> - first paragraph by Paolo, concise problem description
> - rest from Theodore's original commit ("I" = Theodore, I suppose)
> - diff exctly as in gnulib commit
>
> On Mon, Apr 28, 2014 at 11:58:50AM -0700, Junio C Hamano wrote:
>>     Subject: compat/poll: sleep 1 millisecond to avoid busy wait
>
> Thanks for improving it.
>
>>     Signed-off-by: Theodore Leblond <theodore.leblond@gmail.com>
>>     Signed-off-by: Stepan Kasal <kasal@ucw.cz>
>>     Acked-by: Johannes Sixt <j6t@kdbg.org>
>>     Acked-by: Erik Faye-Lund <kusmabite@gmail.com>
>
> Sorry that I forgot to add my sign-off (Stepan).
> But I'm afraid I cannot add Theodore's, it was not in the original
> commit.  But it is one line change; the real work was the analysis.