linux-kernel - Re: [PATCH 6/7] perf: Add support to dynamically get cacheline size

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Date:	Fri, 23 May 2014 13:30:26 -0400
From:	Don Zickus <dzickus@...hat.com>
To:	Jiri Olsa <jolsa@...hat.com>
Cc:	acme@...stprotocols.net, peterz@...radead.org,
	LKML <linux-kernel@...r.kernel.org>, namhyung@...il.com,
	eranian@...gle.com, Andi Kleen <andi@...stfloor.org>
Subject: Re: [PATCH 6/7] perf: Add support to dynamically get cacheline size

On Fri, May 23, 2014 at 07:09:01PM +0200, Jiri Olsa wrote:
> On Mon, May 19, 2014 at 03:13:52PM -0400, Don Zickus wrote:
> 
> SNIP
> 
> > diff --git a/tools/perf/util/cpumap.h b/tools/perf/util/cpumap.h
> > index 61a6548..b3e7b22 100644
> > --- a/tools/perf/util/cpumap.h
> > +++ b/tools/perf/util/cpumap.h
> > @@ -81,4 +81,16 @@ static inline int cpu__get_node(int cpu)
> >  	return cpunode_map[cpu];
> >  }
> >  
> > +int cacheline_size;
> 
> hum, so cacheline_size does not need to be global, if you use
> cpu__cacheline_size in your next patch, right?

I made cpu__cacheline_size an inline so I think it does.  If I stick that
function in cpumap.c then yeah I would agree it would not need to be
global.

Being that is was going to be called repeatedly while processing each
event I opted to make it an inline.  I guess I could change that if it
matters.

> 
> > +
> > +int cpu__setup_cacheline_size(void);
> > +
> > +static inline int cpu__cacheline_size(void)
> > +{
> > +	if (unlikely(!cacheline_size))
> > +		pr_debug("cacheline size not initialized\n");
> > +
> > +	return cacheline_size;
> > +}
> > +
> >  #endif /* __PERF_CPUMAP_H */
> > diff --git a/tools/perf/util/sort.c b/tools/perf/util/sort.c
> > index 635cd8f..50adbfb 100644
> > --- a/tools/perf/util/sort.c
> > +++ b/tools/perf/util/sort.c
> > @@ -2,6 +2,7 @@
> >  #include "hist.h"
> >  #include "comm.h"
> >  #include "symbol.h"
> > +#include "cpumap.h"
> >  
> >  regex_t		parent_regex;
> >  const char	default_parent_pattern[] = "^sys_|^do_page_fault";
> > @@ -1117,6 +1118,8 @@ int setup_sorting(void)
> >  		return -ENOMEM;
> >  	}
> >  
> > +	cpu__setup_cacheline_size();
> > +
> 
> I dont think this is the best place to call the setup,
> on the other hand I can't think of any suitable ;-)
> 
> how about lazy initialization from cpu__cacheline_size?
> 
> We also have page_size variable which gets initialized
> in main and is globaly accesable. I wonder we should
> add the cacheline_size variable in the same way.

That seems to make sense.  I can stick the variable in util.c|h then?

Cheers,
Don
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