* [PATCH] epoll: add EPOLLEXCLUSIVE constant and documentation
@ 2017-03-18 0:56 Eric Wong
0 siblings, 0 replies; only message in thread
From: Eric Wong @ 2017-03-18 0:56 UTC (permalink / raw)
To: sleepy-penguin
I'm still not convinced this is necessary, but it's in Linux, now,
and maybe some folks will want it.
My position remains: Never put listen sockets in epoll if
you're using threads; instead, dedicate a thread to doing
nothing but _blocking_ accept4 + epoll_ctl(.. EPOLL_CTL_ADD).
Of course, if you're using something which does not have
native thread support but using multiple processes, then
yes, EPOLLEXCLUSIVE will prevent multiple processes from
turning into a thundering herd.
In other words: I would use this with Perl5, but not with Ruby 1.9+ :P
---
ext/sleepy_penguin/epoll.c | 11 +++++++++++
1 file changed, 11 insertions(+)
diff --git a/ext/sleepy_penguin/epoll.c b/ext/sleepy_penguin/epoll.c
index 8155c4a..09c4bf7 100644
--- a/ext/sleepy_penguin/epoll.c
+++ b/ext/sleepy_penguin/epoll.c
@@ -306,6 +306,17 @@ void sleepy_penguin_init_epoll(void)
rb_define_const(cEpoll, "WAKEUP", UINT2NUM(EPOLLWAKEUP));
#endif
+#ifdef EPOLLEXCLUSIVE
+ /*
+ * Sets an exclusive wakeup mode for the epoll object
+ * that is being attached to the target IO. This
+ * avoids thundering herd scenarios when the same
+ * target IO is shared among multiple epoll objects.
+ * Available since Linux 4.5
+ */
+ rb_define_const(cEpoll, "EXCLUSIVE", UINT2NUM(EPOLLEXCLUSIVE));
+#endif
+
/* watch for urgent read(2) data */
rb_define_const(cEpoll, "PRI", UINT2NUM(EPOLLPRI));
--
EW
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2017-03-18 0:56 [PATCH] epoll: add EPOLLEXCLUSIVE constant and documentation Eric Wong
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