Messages in this thread | | | Date | Thu, 24 Sep 2009 20:38:20 -0400 | From | Chris Mason <> | Subject | Re: regression in page writeback |
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On Fri, Sep 25, 2009 at 10:11:17AM +1000, Dave Chinner wrote: > On Thu, Sep 24, 2009 at 11:15:08AM +0800, Wu Fengguang wrote: > > On Wed, Sep 23, 2009 at 10:00:58PM +0800, Chris Mason wrote: > > > The only place that actually honors the congestion flag is pdflush. > > > It's trivial to get pdflush backed up and make it sit down without > > > making any progress because once the queue congests, pdflush goes away. > > > > Right. I guess that's more or less intentional - to give lowest priority > > to periodic/background writeback. > > IMO, this is the wrong design. Background writeback should > have higher CPU/scheduler priority than normal tasks. If there is > sufficient dirty pages in the system for background writeback to > be active, it should be running *now* to start as much IO as it can > without being held up by other, lower priority tasks.
I'd say that an fsync from mutt or vi should be done at a higher prio than a background streaming writer.
-chris
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