Messages in this thread | | | Date | Sat, 5 May 2007 12:00:29 -0700 (PDT) | From | Davide Libenzi <> | Subject | Re: [PATCH] rfc: threaded epoll_wait thundering herd |
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On Fri, 4 May 2007, Davi Arnaut wrote:
> Hi, > > If multiple threads are parked on epoll_wait (on a single epoll fd) and > events become available, epoll performs a wake up of all threads of the > poll wait list, causing a thundering herd of processes trying to grab > the eventpoll lock. > > This patch addresses this by using exclusive waiters (wake one). Once > the exclusive thread finishes transferring it's events, a new thread > is woken if there are more events available. > > Makes sense?
Theorically, make sense. I said theorically because all the use epoll_wait MT use cases I've heard of, use a single thread that does the epoll_wait, and then dispatch to worker threads. So thundering herd is not in the picture. OTOH, it does not hurt either. But, that code is completely changed with the new single-pass epoll delivery code that is in -mm. So, I'd either wait for that code to go in, or I (or you, if you like) can make a patch against -mm.
- Davide
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