linux-kernel - Re: [PATCH 31/48] uv: Replace __get_cpu

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Message-ID: <alpine.DEB.2.10.1403071214560.22377@nuc>
Date:	Fri, 7 Mar 2014 12:16:45 -0600 (CST)
From:	Christoph Lameter <cl@...ux.com>
To:	Mike Travis <travis@....com>
cc:	Andrew Morton <akpm@...ux-foundation.org>,
	Tejun Heo <tj@...nel.org>, akpm@...uxfoundation.org,
	rostedt@...dmis.org, linux-kernel@...r.kernel.org,
	Ingo Molnar <mingo@...nel.org>,
	Peter Zijlstra <peterz@...radead.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	Hedi Berriche <hedi@....com>,
	Dimitri Sivanich <sivanich@....com>
Subject: Re: [PATCH 31/48] uv: Replace __get_cpu_var

On Wed, 5 Mar 2014, Mike Travis wrote:

> I haven't had much chance yet to look over your proposed changes but
> FYI, the counters are strictly feedback to insure that there are not
> unhandled NMI events from the perf subsystem.  The exact count is
> irrelevant.  IOW, counts in the double or triple digits is okay,
> counts > 100,000 is definitely not okay (there are multiple millions
> of perf events every 'perf top' refresh.)
>
> I'm not sure if this alters how you want to approach the changes.

Gotta patch here that converts all the atomic per cpu counters to int but
the local64_t definitions look very strange to me. I have never seen a
local64_t definition that is global and used for a counters. That can only
work if there is only one and exactly one processor that is modifying the
count.

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