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From: Sean Bruno <seanbru@yahoo-inc.com>
To: Julian Elischer <julian@freebsd.org>
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References: <1285601161.7245.7.camel@home-yahoo> <4CA0BE08.50408@freebsd.org>
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Date: Mon, 27 Sep 2010 09:21:56 -0700
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Cc: "sbruno@freebsd.org" <sbruno@freebsd.org>,
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Subject: Re: MAXCPU preparations
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On Mon, 2010-09-27 at 08:53 -0700, Julian Elischer wrote:
> On 9/27/10 8:26 AM, Sean Bruno wrote:
> > Does this look like an appropriate modification to libmemstat?
> >
> > Sean
> >
> >
> > ==== //depot/yahoo/ybsd_7/src/lib/libmemstat/memstat.h#4
> > - /home/seanbru/ybsd_7/src/lib/libmemstat/memstat.h ====
> > @@ -28,12 +28,13 @@
> >
> >   #ifndef _MEMSTAT_H_
> >   #define        _MEMSTAT_H_
> > +#include<sys/param.h>
> >
> >   /*
> >    * Number of CPU slots in library-internal data structures.  This
> > should be
> >    * at least the value of MAXCPU from param.h.
> >    */
> > -#define        MEMSTAT_MAXCPU  64
> > +#define        MEMSTAT_MAXCPU  MAXCPU /* defined in
> > sys/${ARCH}/include/param.h */
> >
> 
> 
> wouldn't it be better to do a sysctlbyname() and use the real value 
> for the system?
> 

That was my initial thought (as prodded by scottl and peter).  

If it is made dynamic, could this be opening a race condition where the
call to sysctlbyname() returns a count of CPUS that is in turn changed
by the offlining of a CPU?  Or am I thinking to much about this?

Sean