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Date: Wed, 22 Jun 2011 09:01:39 +0200 From: Jens Axboe <jaxboe@...ionio.com> To: Peter Zijlstra <a.p.zijlstra@...llo.nl> CC: "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>, Linus Torvalds <torvalds@...ux-foundation.org>, Ingo Molnar <mingo@...e.hu>, Thomas Gleixner <tglx@...utronix.de>, Tejun Heo <tj@...nel.org> Subject: Re: [RFC][PATCH 1/3] sched, block: Move unplug On 2011-06-22 01:34, Peter Zijlstra wrote: > Thomas found that we're doing a horrendous amount of work in that scheduler > unplug hook while having preempt and IRQs disabled. > > Move it to the head of schedule() where both preemption and IRQs are enabled > such that we don't get these silly long IRQ/preempt disable times. > > This allows us to remove a lot of special magic in the unplug path, > simplifying that code as a bonus. The major change here is moving the queue running inline, instead of punting to a thread. The worry is/was that we risk blowing the stack if something ends up blocking inadvertently further down the call path. Since it's the unlikely way to unplug, a bit of latency was acceptable to prevent this problem. I'm curious why you made that change? It seems orthogonal to the change you are actually describing in the commit message. -- Jens Axboe -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.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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