* [PATCH] doc: design_notes: we do not use EPOLLEXCLUSIVE
@ 2017-03-18 0:54 Eric Wong
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From: Eric Wong @ 2017-03-18 0:54 UTC (permalink / raw)
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
@@ -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.
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2017-03-18 0:54 [PATCH] doc: design_notes: we do not use EPOLLEXCLUSIVE Eric Wong
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