Re: [PATCH 4/4] writeback: Reporting dirty thresholds in/proc/vmstat

[Wu Fengguang]

> Right now we don't mount all of debugfs at boot time. We have not done
> the work to verify its safe in our environment. It's mostly a nit.

You work discreetly, that's a good thing. Note that most
sub-directories under debugfs can be turned off in kconfig.

> Also I was under the impression that debugfs was intended more for
> kernel devs while /proc and /sys was intended for application
> developers.

I guess the keyword here is "debugging/diagnosing". Think about
/debug/tracing. DirtyThresh seems like the same stuff.

> >> 3) Full system counters are easier to handle the juggling of removable
> >> storage where these numbers will appear and disappear due to being
> >> dynamic.
> 
> This is the biggie to me. The idea is to get a complete view of the
> system's writeback behaviour over time. With systems with hot plug
> devices, or many many drives collecting that view gets difficult.

Sorry for giving a wrong example. Hope this one is better:

$ cat /debug/bdi/default/stats
[...]
DirtyThresh:       1838904 kB
BackgroundThresh:   919452 kB
[...]

It's a trick to avoid messing with real devices :)

Thanks,
Fengguang
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