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Re: [dm-devel] Re: fastfail operation and retries



On 4/27/05, Lars Marowsky-Bree <lmb suse de> wrote:
> User-space needs to take action and tell us when to stop queuing.

Is there any risk of priority inversion?  I can't think of a specific
issue beyond the userspace daemon process simply not existing that
wouldn't hopefully settle out over time and I haven't looked closely
at this aspect of 2.6, but it used to be easy to get/keep the cpu busy
enough on flushing IO to disk to hurt userspace response times (fibre
pulls during heavy buffered, filesystem IO effectively DoSing the
machine for a long period).  If that sort of thing is still possible,
it seems risky relying on a userspace application for
timely/meaningful recovery of the resources consumed by the IO.


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