Re: [PATCH 3/4] vmstat: add anon_scan_ratio field to zoneinfo

[KOSAKI Motohiro]

> * KOSAKI Motohiro <kosaki.motohiro@xxxxxxxxxxxxxx> [2009-12-28 16:48:51]:
> 
> > Vmscan folks was asked "why does my system makes so much swap-out?"
> > in lkml at several times.
> > At that time, I made the debug patch to show recent_anon_{scanned/rorated}
> > parameter at least three times.
> > 
> > Thus, its parameter should be showed on /proc/zoneinfo. It help
> > vmscan folks debugging.
> >
> 
> Hmmm.. I think this should come under DEBUG_VM, a lot of tools use
> /proc/zoneinfo, the additional overhead may be high.. no? Also,
> I would recommend adding the additional details to the end, so
> as to not break existing tools (specifically dump line # based
> tools).

Thanks, I have three answer. 1)  I really hope to don't enclose DEBUG_VM. otherwise 
my harm doesn't solve. 2) but your performance worry is fair enough. I plan to remove 
to grab zone->lru_lock in reading /proc/zoneinfo. 3)  append new line doesn't break 
existing tools. because zoneinfo show vmstat and we often append new vmstat in past 
years. but I haven't seen zoneinfo breakage bug report. because zoneinfo file show 
multiple zone information, then nobody access it by line number.





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