Messages in this thread | | | Subject | Re: 2 epoll questions | From | Eric Dumazet <> | Date | Tue, 30 Nov 2010 08:03:51 +0100 |
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Le lundi 29 novembre 2010 à 19:17 -0500, Mike Blumenkrantz a écrit : > Hi, > > I am not subscribed to the list yet, and I would appreciate it if all replies > could be CCed to me :). > > I have two questions regarding epoll. The epoll code that I am using can all > be found in the file here for those interested: > https://svn.enlightenment.org/svn/e/trunk/ecore/src/lib/ecore/ecore_main.c > > 1) Is there any known reason why adding fds to an epoll fd would begin to slow > down dramatically after ~6000 fds are added? It is entirely possible that the > problem is not epoll at all, but I wanted to ask and see if there was some O(n) > code somewhere that was known. >
No particular slowdown, I once used more than 1.5 million fds in epoll fd.
Of course, if you only add/remove fds as fast as possible, its going to be slower, since epoll fds are stored in a tree, and the time of insert/delete of one item depends on the tree depth. Maybe this is your case and your working set is larger than your cpu caches after ~6000 fds ?
> 2) If a select on an epoll fd (not one inside the epoll, the actual epoll fd > itself) returns EBADF, is there a way to determine which fd is causing the > error and then remove it? I am occasionally running into this issue, and it > seems to be caused by code which I do not necessarily control closing a fd that > is part of my epoll fd without my knowledge (meaning that the closed fd is > still in epoll).
Strange, I never got this EBADF error. On epoll_ctl() or epoll_wait() ? (I dont understand your "select on epoll fd"). epoll is meant to replace select()...
When you close a file descriptor, its automatically removed from epoll as well.
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