From mboxrd@z Thu Jan  1 00:00:00 1970
From: Zoltan Menyhart <Zoltan.Menyhart@bull.net>
Date: Mon, 03 Apr 2006 16:33:38 +0000
Subject: Re: accessed/dirty bit handler tuning
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To: linux-ia64@vger.kernel.org

Luck, Tony wrote:
>>It is very much curious having so few dirty and i-access traps...
> 
> 
> Your data collection code has races (ld8, add, st8 on one cpu can
> race with another cpu doing the same).  So you'll undercount whenever
> a race happens.
> 
> Perhaps you should use per-cpu counters to collect the values, and
> then sum for each cpu in the syscall() before reporting to the user?

It was not very important to count the events precisely.

The lesson I learnt is the VHPT miss handler is the most important
(maybe the D-ACCESS trap handler), the others are "neglectable".
(I have not counted yet the handlers not doing a purge.)

The problem is that the most frequently used trap handler contains
the unsafe walk of the

	rx = IA64_KR_PT_BASE -> pgd[i] -> pud[j] -> pmd[k] -> pte[l]

chain...

Zoltan