linux-kernel - Re: [PATCH 3/4] perf tool: Fix build when sysconf doesn't support cache line size

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Message-ID: <20160704224832.GZ5324@kernel.org>
Date:	Mon, 4 Jul 2016 19:48:32 -0300
From:	Arnaldo Carvalho de Melo <acme@...nel.org>
To:	Chris Phlipot <cphlipot0@...il.com>
Cc:	peterz@...radead.org, mingo@...hat.com,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 3/4] perf tool: Fix build when sysconf doesn't support
 cache line size

Em Thu, Jun 30, 2016 at 10:12:34PM -0700, Chris Phlipot escreveu:
> Enable perf to build on libc implementations where sysconf() doesn't
> support _SC_LEVEL1_DCACHE_LINESIZE as a parameter.
> 
> For example, the Bionic implementation does not support this as a
> paremter. Older versions of Bionic will throw an error when this is passed
> in as a parameter, and more recent versions will just return 0 as the
> cache line size.
> 
> Signed-off-by: Chris Phlipot <cphlipot0@...il.com>
> ---
>  tools/perf/perf.c | 4 ++++
>  1 file changed, 4 insertions(+)
> 
> diff --git a/tools/perf/perf.c b/tools/perf/perf.c
> index 8f21922..113ca5b 100644
> --- a/tools/perf/perf.c
> +++ b/tools/perf/perf.c
> @@ -509,7 +509,11 @@ int main(int argc, const char **argv)
>  
>  	/* The page_size is placed in util object. */
>  	page_size = sysconf(_SC_PAGE_SIZE);
> +#ifdef _SC_LEVEL1_DCACHE_LINESIZE
>  	cacheline_size = sysconf(_SC_LEVEL1_DCACHE_LINESIZE);
> +#else
> +	cacheline_size = 0;
> +#endif

Couldn't we instead fallback to:

sysfs__read_int("devices/system/cpu/cpu0/cache/index0/coherency_line_size", &cacheline_size)

?
  
>  	if (sysctl__read_int("kernel/perf_event_max_stack", &value) == 0)
>  		sysctl_perf_event_max_stack = value;
> -- 
> 2.7.4