[PATCH] doc: design_notes: we do not use EPOLLEXCLUSIVE

[PATCH] doc: design_notes: we do not use EPOLLEXCLUSIVE

[Eric Wong]

And clarify that we only have one thread by default.

Since EPOLLEXCLUSIVE seems to have gotten some more press, I
guess we should emphasize our design does not rely on it.
---
 Documentation/design_notes.txt | 9 ++++++---
 1 file changed, 6 insertions(+), 3 deletions(-)

diff --git a/Documentation/design_notes.txt b/Documentation/design_notes.txt
index 308faa6..68d31bc 100644
--- a/Documentation/design_notes.txt
+++ b/Documentation/design_notes.txt
@@ -17,9 +17,12 @@ socket we have inside the kernel.
 Each listen queue has a dedicated thread pool running _blocking_
 accept(2) (or accept4(2)) syscall in a loop.  We use dedicated threads
 and blocking accept to benefit from "wake-one" behavior in the Linux
-kernel.  By default, this thread pool only has thread per-process, doing
+kernel.  By default, this thread pool only has one thread per-process, doing
 nothing but accepting sockets and injecting into to the event queue
-(used by epoll or kqueue).
+(used by epoll or kqueue) so a worker thread pool can pick them up.
+
+This design makes EPOLLEXCLUSIVE in Linux 4.5+ unnecessary to us,
+our listen sockets are never registered with epoll or kqueue.
 
 worker thread pool
 ------------------
@@ -38,7 +41,7 @@ allows us to guarantee exclusive access to a client socket without
 additional locks managed in userspace.
 
 Idle threads will sit performing epoll_wait(2) (or kevent(2))
-indefinitely until a socket is reported as "ready" by the kernel.
+indefinitely until a client socket is reported as "ready" by the kernel.
 
 queue flow
 ----------
-- 
EW