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Subject: RE: [PATCH 0/5] Some vmevent fixes...
Thread-Topic: [PATCH 0/5] Some vmevent fixes...
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> -----Original Message-----
> From: penberg@gmail.com [mailto:penberg@gmail.com] On Behalf Of ext
> Pekka Enberg
> Sent: 05 June, 2012 11:02
> To: Minchan Kim
...
> > Next concern is that periodic timer of implementation.
> > I think it would add direct hook in vmscan.c rather than peeking raw
> > vmstat periodically by timer so we can control more fine-grained way
> without unnecessary overhead.
> 
> If the hooks are clean and it doesn't hurt the  !CONFIG_VMEVENT case, I'm
> completely OK with that.

On the previous iteration hooking vm was pointed as very bad idea, so in my version I installed shrinker to handle cases when we have memory pressure.
Using deferred timer with adequate timeout (0.250 ms or larger) fully suitable for userspace and produce adequate overhead 
-> by nature such API should not be 100% accurate, anyhow applications cannot handle situation as good as kernel can provide, 0.5MB space accuracy, 100ms is maximum user-space require for 64-1024MB devices.