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Message-ID: <20111020212958.GA25124@google.com> Date: Thu, 20 Oct 2011 14:29:58 -0700 From: Tejun Heo <tj@...nel.org> To: Vivek Goyal <vgoyal@...hat.com> Cc: linux-kernel@...r.kernel.org, jaxboe@...ionio.com Subject: Re: [PATCH 2/2] blk-throttle: Take blkcg->lock while traversing blkcg->policy_list Hello, On Thu, Oct 20, 2011 at 05:20:21PM -0400, Vivek Goyal wrote: > The only problem with this approach is that it will cleanup per device > weight rules also at elevator_exit() time which is not same as device > removal and one might device to bring CFQ back on device and we will > need the rules again. I actually think removoing those rules on elevator detach would be the right thing to do. We don't try to keep cfq setting across elevator switch. When we're switching from cfq, we're detaching iocg policy too. The settings going away is perfectly fine. I actually think it's a pretty bad idea to implement ad-hoc setting persistence in kernel. Just making sure that userland is notified is far better approach. Userland has all the facilities to deal with this type of situations. When switching from cfq to deadline, we lose the whole proportional io control. It's way more confusing to have lingering settings which don't do anything. Thanks. -- tejun -- 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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