linux-kernel - Re: Why do we still have 32 bit counters? Interrupt counters overflow within 50 days

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Message-ID: <20141006193448.GB8238@khazad-dum.debian.net>
Date:	Mon, 6 Oct 2014 16:34:48 -0300
From:	Henrique de Moraes Holschuh <hmh@....eng.br>
To:	Thomas Gleixner <tglx@...utronix.de>
Cc:	Christoph Lameter <cl@...ux.com>,
	Richard Cochran <richardcochran@...il.com>,
	linux-kernel@...r.kernel.org
Subject: Re: Why do we still have 32 bit counters? Interrupt counters
 overflow within 50 days

> > Tools expect the number of interrupt to increase linearly and not jump by
> > 2^32 once in awhile. There are functions in the kernel (/proc/stat) that

...

> I understand that, I just wonder why nobody noticed before. It's been
> that way forever :)

Any proper tool that interfaces to snmp-like counters expects and deals with
worse: sudden counter resets.

And it has been that way forever :-)  So people who use such tools would
hardly notice any warp-arounds...

So, the question becomes: which tools are misbehaving?  Maybe they should
adopt snmp-like counter reset detection for peak filtering, and we could
leave 32-bit alone, and increase the counter size only on for 64-bit?

-- 
  "One disk to rule them all, One disk to find them. One disk to bring
  them all and in the darkness grind them. In the Land of Redmond
  where the shadows lie." -- The Silicon Valley Tarot
  Henrique Holschuh
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