- Python 2.7.3 - [twisted, version 13.1.0] - xen-domU `atop` shows that `carbon-relay` is eating 80, 90% USRCPU. From the `strace`: accept(7, {sa_family=AF_INET, sin_port=htons(60649), sin_addr=inet_addr("192.237.222.81")}, [16]) = 257 accept(7, {sa_family=AF_INET, sin_port=htons(51564), sin_addr=inet_addr("166.78.1.48")}, [16]) = 257 accept(7, 0x7ffff4679550, [16]) = -1 EAGAIN (Resource temporarily unavailable) accept(7, {sa_family=AF_INET, sin_port=htons(33654), sin_addr=inet_addr("198.61.194.248")}, [16]) = 257 accept(7, {sa_family=AF_INET, sin_port=htons(50037), sin_addr=inet_addr("166.78.181.204")}, [16]) = 257 accept(7, 0x7ffff4679550, [16]) = -1 EAGAIN (Resource temporarily unavailable) The strange thing is: even restart the service, it seems stuck at fd 7 everytime running `strace`. Does it mean this fd is not being cleanup properly? I have increased the number of open files: **/proc/2891/limits** Limit Soft Limit Hard Limit Units Max cpu time unlimited unlimited seconds Max file size unlimited unlimited bytes Max data size unlimited unlimited bytes Max stack size 8388608 unlimited bytes Max core file size 0 unlimited bytes Max resident set unlimited unlimited bytes Max processes 15834 15834 processes Max open files 16384 16384 files Max locked memory 65536 65536 bytes Max address space unlimited unlimited bytes Max file locks unlimited unlimited locks Max pending signals 15834 15834 signals Max msgqueue size 819200 819200 bytes Max nice priority 0 0 Max realtime priority 0 0 Max realtime timeout unlimited unlimited us then it decreases down to ~ 50%. My problem looks like similar to this [thread]( http://twistedmatrix.com/pipermail/twisted-python/2008-September/018361.html) but since we have a few sockets in TIME_WAIT state, I don't think that enable the `tw_recycle` can help. About the `tcp_syncookies`, I don't see any related message in the syslog. This is what I get when trying to start `carbon-relay` in debug mode: 26/11/2013 02:22:14 :: [listener] MetricPickleReceiver connection with 50.56.249.127:48772 lost: Connection to the other side was lost in a non-clean fashion: Connection lost. 26/11/2013 02:22:14 :: [listener] MetricPickleReceiver connection with 198.101.241.101:50672 lost: Connection to the other side was lost in a non-clean fashion: Connection lost. 26/11/2013 02:22:14 :: [listener] MetricPickleReceiver connection with 166.78.2.167:43346 lost: Connection to the other side was lost in a non-clean fashion: Connection lost. This is from `twisted`: class ConnectionLost(ConnectionClosed): """Connection to the other side was lost in a non-clean fashion""" def __str__(self): s = self.__doc__.strip().splitlines()[0] if self.args: s = '%s: %s' % (s, ' '.join(self.args)) s = '%s.' % s return s I also have tried to [debug with `gdb`]( https://wiki.python.org/moin/DebuggingWithGdb) but `pystack` returns nothing.