Re: [PATCH 5/5] writeback: Reporting dirty thresholds in/proc/vmstat

[Andrew Morton]

On Sun, 12 Sep 2010 22:58:13 -0700
Michael Rubin <mrubin@xxxxxxxxxx> 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
> 

Yes, I think /proc/vmstat is a decent place to put these.  The needed
infrastructural support is minimal and although these numbers are
closely tied to the implementation-of-the-day, people should expect
individual fields in /proc/vmstat to appear and disappear at random as
kernel versions change.

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