* Jason Baron <jba...@akamai.com> wrote:
> Hi,
>
> 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 a new EPOLL_ROTATE
> flag to allow for round robin exclusive wakeups.
>
> I believe this patch series addresses the two main
> concerns that were raised in prior postings. Namely, that
> it affected code (and potentially performance) of the
> core kernel wakeup functions, even in cases where it was
> not strictly needed, and that it could lead to wakeup
> starvation (since we were are no longer waking up all
> waiters). It does so by adding an extra layer of
> indirection, whereby waiters are attached to a 'psuedo'
> epoll fd, which in turn is attached directly to the
> wakeup source.
> sched/wait: add __wake_up_rotate()
> include/linux/wait.h | 1 +
> kernel/sched/wait.c | 27 ++++++++++++++++++++++
So the scheduler bits are looking good to me in principle,
because they just add a new round-robin-rotating wakeup
variant and don't disturb the others.
Is there consensus on the epoll ABI changes? With Davide
Libenzi inactive eventpoll appears to be without a
dedicated maintainer since 2011 or so. Is there anyone who
knows the code and its usages in detail and does final ABI
decisions on eventpoll - Andrew, Al or Linus?
Thanks,
Ingo
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