[PATCH v2 0/2] Add epoll round robin wakeup mode

Jason Baron
2015-02-17T19:33:38Z

When we are sharing a wakeup source among multiple epoll fds, we end up with
thundering herd wakeups, since there is currently no way to add to the
wakeup source exclusively. This series introduces 2 new epoll flags,
EPOLLEXCLUSIVE for adding to a wakeup source exclusively. And EPOLLROUNDROBIN
which is to be used in conjunction to EPOLLEXCLUSIVE to evenly
distribute the wakeups. This patch was originally motivated by a desire to
improve wakeup balance and cpu usage for a listen socket() shared amongst
multiple epoll fd sets.

See: http://lwn.net/Articles/632590/ for previous test program and testing
resutls.

Epoll manpage text:

EPOLLEXCLUSIVE
Provides exclusive wakeups when attaching multiple epoll fds to a
shared wakeup source. Must be specified with an EPOLL_CTL_ADD operation.

EPOLLROUNDROBIN
Provides balancing for exclusive wakeups when attaching multiple epoll
fds to a shared wakeup soruce. Depends on EPOLLEXCLUSIVE being set and
must be specified with an EPOLL_CTL_ADD operation.

Thanks,

-Jason

Jason Baron (2):
sched/wait: add round robin wakeup mode
epoll: introduce EPOLLEXCLUSIVE and EPOLLROUNDROBIN

fs/eventpoll.c | 25 ++++++++++++++++++++-----
include/linux/wait.h | 11 +++++++++++
include/uapi/linux/eventpoll.h | 6 ++++++
kernel/sched/wait.c | 10 ++++++++--
4 files changed, 45 insertions(+), 7 deletions(-)

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1.8.2.rc2