On Thu, Aug 19, 2010 at 01:57:26PM -0700, Michael Rubin wrote:
> To help developers and applications gain visibility into writeback
> behaviour adding four read only sysctl files into /proc/sys/vm.
> These files allow user apps to understand writeback behaviour over time
> and learn how it is impacting their performance.
>
> # cat /proc/sys/vm/pages_dirtied
> 3747
> # cat /proc/sys/vm/pages_entered_writeback
> 3618
As Rik said, /proc/sys is not a suitable place.
Frankly speaking I've worked on writeback for years and never felt
the need to add these counters. What I often do is:
$ vmmon -d 1 nr_writeback nr_dirty nr_unstable
nr_writeback nr_dirty nr_unstable
68738 0 39568
66051 0 42255
63406 0 44900
60643 0 47663
57954 0 50352
55264 0 53042
52592 0 55715
49922 0 58385
That is what I get when copying /dev/zero to NFS.
You can find vmmon.c in Andrew Morton's ext3-tools package.
Also attached for your convenience.
I'm very interested in Google's use case for this patch, and why
the simple /proc/vmstat based vmmon tool is not enough.
Thanks,
Fengguang
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