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From: Michael Rubin on 5 Aug 2010 18:10
On Thu, Aug 5, 2010 at 1:24 PM, Andrew Morton <akpm(a)linux-foundation.org> wrote:
> On Wed, �4 Aug 2010 17:43:24 -0700
> Michael Rubin <mrubin(a)google.com> wrote:
> Wait. �These counters appear in /proc/vmstat. �So why create standalone
> /proc/sys/vm files as well?

I did not know they would show up in /proc/vmstat.

I thought it made sense to put them in /proc/sys/vm since the other
writeback controls are there.
but have no problems just adding them to /prov/vmstat if that makes more sense.

mrubin
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From: Michael Rubin on 5 Aug 2010 20:20
On Thu, Aug 5, 2010 at 4:56 PM, KOSAKI Motohiro
<kosaki.motohiro(a)jp.fujitsu.com> wrote:
> /proc/vmstat already have both.
>
> cat /proc/vmstat |grep nr_dirty
> cat /proc/vmstat |grep nr_writeback
>
> Also, /sys/devices/system/node/node0/meminfo show per-node stat.
>
> Perhaps, I'm missing your point.

These only show the number of dirty pages present in the system at the
point they are queried.
The counter I am trying to add are increasing over time. They allow
developers to see rates of pages being dirtied and entering writeback.
Which is very helpful.

mrubin
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From: Michael Rubin on 6 Aug 2010 03:20
On Thu, Aug 5, 2010 at 1:24 PM, Andrew Morton <akpm(a)linux-foundation.org> wrote:
> Wait. These counters appear in /proc/vmstat. So why create standalone
> /proc/sys/vm files as well?

Andrew I was thinking about this today. And I think there is a case
for keeping the proc files.
Christoph was the one who pointed out to me that is their proper home
and I think he's right. Most if not all the tunables for writeback are
there. When one is trying to find the state of the system's writeback
activity that's the directory. Only having these variables in
/proc/vmstat to me feels like a way to make sure that users who would
need them won't find them unless they are reading source. And these
are folks who aren't reading source.

/proc/vmstat _does_ look like a good place to put the thresholds as it
already has similar values as the thresholds suck as
kswapd_low_wmark_hit_quickly.

mrubin
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