Messages in this thread | ![/](/images/icornerl.gif) | | From | Changli Gao <> | Date | Wed, 28 Apr 2010 19:17:29 +0800 | Subject | Re: [RFC] sched: implement the exclusive wait queue as a LIFO queue |
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On Wed, Apr 28, 2010 at 5:29 PM, David Howells <dhowells@redhat.com> wrote: > Changli Gao <xiaosuo@gmail.com> wrote: > >> If there isn't enough work to be done, we'd better not disrupt them >> and leave them sleeping forever to keep the scheduler happier. Do we >> have reason to keep fair to all the workers? Does it have benefit? > > You've made one important assumption: the processes on the wait queue are > sleeping waiting to service things... but what if the wait queue governs > access to a resource, and all the processes on that wait queue need access to > that resource to do things? Some of the processes waiting for it may never > get a go, and so necessary work may be left undone. >
You are right. I made the wrong assumption. But we indeed need some primitive to add wait_queue at the head of the wait_queue_head, and I know epoll needs it, at least.
fs/eventpoll.c: 1443. wait.flags |= WQ_FLAG_EXCLUSIVE; __add_wait_queue(&ep->wq, &wait);
-- Regards, Changli Gao(xiaosuo@gmail.com) -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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