Messages in this thread | | | Date | Tue, 9 Aug 2011 06:47:42 +0800 | From | Wu Fengguang <> | Subject | Re: [PATCH 2/5] writeback: dirty position control |
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On Mon, Aug 08, 2011 at 10:31:49PM +0800, Peter Zijlstra wrote: > On Mon, 2011-08-08 at 22:11 +0800, Wu Fengguang wrote: > > It's actually dead code because (origin < limit) should never happen. > > I feel so good being able to drop 5 more lines of code :) > > OK, but that leaves me trying to figure out what origin is, and why its > 4 * thresh.
origin is where the control line crosses the X axis (in both the global/bdi setpoint cases).
"4 * thresh" is merely something larger than max(dirty, thresh) that yields reasonably gentle slope. The more slope, the larger "gravity" to bring the dirty pages back to the setpoint.
> I'm having a horrible time understanding this stuff.
Sorry for that. Do you have more questions?
Thanks, Fengguang
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