Re: The timerfd functions slow down emacs

[Corinna Vinschen <corinna-cygwin at cygwin dot com>]

On Feb 23 21:24, Ken Brown wrote:
> On 2/23/2019 4:01 PM, Corinna Vinschen wrote:
> > On Feb 23 20:48, Ken Brown wrote:
> >> On 2/23/2019 2:15 PM, Corinna Vinschen wrote:
> >>> Below's the NSSTC I used to test my timerfd implementation (based on
> >>> another STC to show a problem in POSIX timers).  From what I can tell it
> >>> works as desired.  If you find a problem, please point it out or send a
> >>> patch.
> >>
> >> Thanks, that saved me a lot of time.  I was in the process of creating a test
> >> case when your mail arrived.
> >>
> >> Your test works fine.  For example:
> >>
> >> $ gcc timerfd_test.c -o timerfd_test
> >>
> >> $ ./timerfd_test.exe 3 1 10
> >> 0.000: timer started 52379
> >> 2.988: 52379 read: 1; total=1
> >> 3.988: 52379 read: 1; total=2
> >> 4.989: 52379 read: 1; total=3
> >> 5.987: 52379 read: 1; total=4
> >> 7.001: 52379 read: 1; total=5
> >> 7.987: 52379 read: 1; total=6
> >> 9.001: 52379 read: 1; total=7
> >> 9.987: 52379 read: 1; total=8
> >> 10.987: 52379 read: 1; total=9
> >> 11.997: 52379 read: 1; total=10
> >>
> >> But if I change CLOCK_MONOTONIC by CLOCK_REALTIME in the call to timerfd_create,
> >> then I get the following:
> > 
> > Only in timerfd_create?  Not in clock_gettime?  If you don't
> > do that, you're using a different clock with entirely different
> > values for the starttime.
> > 
> > Actually, this testcase started with CLOCK_REALTIME in both calls.
> > If I revert to that, I get:
> > 
> > )$ ./timerfd 3 1 10
> > 0.000: timer started 644
> > 3.001: 644 read: 1; total=1
> > 4.001: 644 read: 1; total=2
> > 5.017: 644 read: 1; total=3
> > 6.001: 644 read: 1; total=4
> > 7.001: 644 read: 1; total=5
> > 8.009: 644 read: 1; total=6
> > 9.002: 644 read: 1; total=7
> > 10.001: 644 read: 1; total=8
> > 11.010: 644 read: 1; total=9
> > 12.017: 644 read: 1; total=10
> > 
> > I tested this STC with differnt clocks, but it's important to
> > use the same cloack for clock_gettime and timerfd_create.
> 
> Yes, that was careless of me.  I now get the same results as you.  I'll have to 
> go back to the emacs sources and see what else might be different there.

You're right, nevertheless.  Select on timerfd returns immediately.
I (hope I) fixed that in git and uploaded new developer snapshots to
https://cygwin.com/snapshots/

Please try especially with emacs.

If that works as desired, I release 3.0.2 pretty soon.


Thanks,
Corinna

-- 
Corinna Vinschen
Cygwin Maintainer

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