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

[Wu Fengguang]

On Fri, Aug 20, 2010 at 05:31:29PM +0800, Michael Rubin wrote:
> The kernel already exposes the user desired thresholds in /proc/sys/vm
> with dirty_background_ratio and background_ratio. But the kernel may
> alter the number requested without giving the user any indication that
> is the case.
> 
> Knowing the actual ratios the kernel is honoring can help app developers
> understand how their buffered IO will be sent to the disk.
> 
> 	$ grep threshold /proc/vmstat
> 	nr_dirty_threshold 409111
> 	nr_dirty_background_threshold 818223

I realized that the dirty thresholds has already been exported here:

$ grep Thresh  /debug/bdi/8:0/stats
BdiDirtyThresh:     381000 kB
DirtyThresh:       1719076 kB
BackgroundThresh:   859536 kB

So why not use that interface directly?

Thanks,
Fengguang
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