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

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Message-Id: <cover.1424200151.git.jbaron@akamai.com>
Date:	Tue, 17 Feb 2015 19:33:36 +0000 (GMT)
From:	Jason Baron <jbaron@...mai.com>
To:	peterz@...radead.org, mingo@...hat.com, viro@...iv.linux.org.uk
Cc:	akpm@...ux-foundation.org, normalperson@...t.net,
	davidel@...ilserver.org, mtk.manpages@...il.com,
	linux-kernel@...r.kernel.org, linux-fsdevel@...r.kernel.org,
	linux-api@...r.kernel.org
Subject: [PATCH v2 0/2] Add epoll round robin wakeup mode

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(-)

-- 
1.8.2.rc2

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