[TIP] Intent to implement epoll()/kqueue() support for sockets on Linux/FreeBSD

[lalbornoz]

Nov 23 4:30 PM:
epoll() support on Linux in the event loop (tclUnixNotfy.c) implemented; some testing done.
Nov 23 6:04 PM:
kqueue/kevent() support on FreeBSD in the event loop (tclUnixNotfy.c): code written, compiles.
Nov 23 7:52 PM:
Cleanup; refactored code into four subroutines. Now commencing testing/bugfixing.
Nov 24 12:16 PM:
Code review; will contact tcl-core tomorrow.
Nov 24 4:19 PM:
Preliminarily pushed to https://github.com/lalbornoz/tcl (`epoll' branch.)
Nov 25 1:51 PM:
Initial tcl-core contact.
Nov 25 5:18 PM:
http://www.tcl.tk/cgi-bin/tct/tip/458.html
Dec 6 7:33 PM:
Supports DragonFly/Free/Net/OpenBSD and Linux; running relevant tests/* on those platforms and fixing bugs that come up.

[dkfellows]

http://core.tcl.tk/tcl/timeline?r=tip-458

[lalbornoz]

tests/* now all complete successfully on FreeBSD and Linux as of <96b5aa3016ee4e41b81534fbcccbab168d1a9338>,
with a small number of tests that fail on Tcl v8.6.6 as well as w/ the new code. The output logs of $ make test w/ Tcl v8.6.6 and HEAD on both FreeBSD and Linux can be found in tcl*_tests.log in the Github repository.
The specific issue on FreeBSD appears to be that Linux returns EINPROGRESS for a connect(2) to an address that can synchronously be completed w/ ECONNREFUSED, whereas FreeBSD always returns ECONNREFUSED. This causes TcpConnect() to return TCL_ERROR instead of TCL_OK; the tests however expect either TCL_OK or TCL_RETURN and thus fail.
FYI: the code now lives in the `tip458' branch of https://github.com/lalbornoz/tcl/.

[lalbornoz]

Awaiting feedback/vote/...

[lehenbauer]

OK, we are testing this.

[lalbornoz]

My new code was just committed: http://core.tcl.tk/tcl/info/858569fb0484a15478f8583287a263ac6215f20c. Assuming there are no remaining concerns, I'd like to claim the bounty.

[nijtmans]

TIP vote is done (accepted), and implementation is on trunk (8.7) now. Congratuations!

[bll123]

FYI: The new epoll() code does not work correctly.
https://core.tcl.tk/tcl/tktview?name=1a6a36d901

[lalbornoz]

I've pushed a fix concerning epoll_wait() timeout calculation in lalbornoz/tcl@7249454.
Can you confirm that this reduces CPU usage down to expected values w/ both the busyWait as well as the disconnected sockets tests?

[bll123]

Looks much better.
I ran the busy-wait test, use of dbus package test.

I don't have a specific test built for the disconnected socket, but I pulled up an older copy of my application and it seems ok.

With the patch (busy-wait test):
bll-tecra:bll$ time $HOME/local87/bin/tclsh8.7 t.tcl
^C

real 0m7.413s
user 0m0.029s
sys 0m0.005s

[dkfellows]

Let me guess from the patch; the timeout was meant to be in ms, yet was being fed seconds?

[lalbornoz]

Precisely; the kqueue(2)-based notifier correctly converts between struct time{val,spec} and thus only Linux was/is affected.