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

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Date:	Fri, 23 May 2014 19:09:01 +0200
From:	Jiri Olsa <jolsa@...hat.com>
To:	Don Zickus <dzickus@...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 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?

> +
> +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.

jirka
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