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Date: Wed, 14 Jun 2006 17:40:40 -0500
From: Nathan Lynch <ntl@pobox.com>
To: Paul Mackerras <paulus@samba.org>
Subject: Re: [PATCH 2/3] powerpc: Instrument Hypervisor Calls: add wrappers
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Paul Mackerras wrote:
> Nathan Lynch writes:
> 
> > Without disabling preemption around the mfspr ... update_stats section
> > in these hcall wrappers, you risk updating the stats on the wrong cpu.
> 
> I think we are only looking for total counts and times anyway, so it
> doesn't really matter which cpu updates the stats, as long as the time
> gets accounted on some cpu.  The use of per-cpu counters is just for
> better cache behaviour.

Makes sense... then perhaps the stats shouldn't be exported in per-cpu
files in sysfs, and the kernel should calculate and report the totals
to userspace in some other form.