linux-kernel - Re: [RFC PATCH 1/4] perf: Read cache instance ID when building cache topology

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Date:   Fri, 31 Mar 2023 08:54:51 -0300
From:   Arnaldo Carvalho de Melo <acme@...nel.org>
To:     K Prateek Nayak <kprateek.nayak@....com>
Cc:     linux-perf-users@...r.kernel.org, linux-kernel@...r.kernel.org,
        peterz@...radead.org, mingo@...hat.com, mark.rutland@....com,
        alexander.shishkin@...ux.intel.com, jolsa@...nel.org,
        namhyung@...nel.org, ravi.bangoria@....com, sandipan.das@....com,
        ananth.narayan@....com, gautham.shenoy@....com, eranian@...gle.com
Subject: Re: [RFC PATCH 1/4] perf: Read cache instance ID when building cache
 topology

Em Fri, Mar 31, 2023 at 10:21:14AM +0530, K Prateek Nayak escreveu:
> CPU cache level data currently stores cache level, type, line size,
> associativity, sets, total cache size, and the CPUs sharing the cache.
> Also read and store the cache instance ID from
> "/sys/devices/system/cpu/cpuX/cache/indexY/id" in the cache level data.
> Use instance ID as well when comparing cache levels.

And if a new perf tool is used in an older kernel without this new 'id'
file?

Please check if the file exists, if it doesn't don't fail, just
initialize with a zero, this way the latest perf will be usable in older
kernels.

- Arnaldo
 
> Signed-off-by: K Prateek Nayak <kprateek.nayak@....com>
> ---
>  tools/perf/util/env.h    | 1 +
>  tools/perf/util/header.c | 7 +++++++
>  2 files changed, 8 insertions(+)
> 
> diff --git a/tools/perf/util/env.h b/tools/perf/util/env.h
> index 4566c51f2fd9..d761bfae76af 100644
> --- a/tools/perf/util/env.h
> +++ b/tools/perf/util/env.h
> @@ -17,6 +17,7 @@ struct cpu_topology_map {
>  
>  struct cpu_cache_level {
>  	u32	level;
> +	u32	id;
>  	u32	line_size;
>  	u32	sets;
>  	u32	ways;
> diff --git a/tools/perf/util/header.c b/tools/perf/util/header.c
> index 404d816ca124..5c3f5d260612 100644
> --- a/tools/perf/util/header.c
> +++ b/tools/perf/util/header.c
> @@ -1131,6 +1131,9 @@ static bool cpu_cache_level__cmp(struct cpu_cache_level *a, struct cpu_cache_lev
>  	if (a->level != b->level)
>  		return false;
>  
> +	if (a->id != b->id)
> +		return false;
> +
>  	if (a->line_size != b->line_size)
>  		return false;
>  
> @@ -1168,6 +1171,10 @@ static int cpu_cache_level__read(struct cpu_cache_level *cache, u32 cpu, u16 lev
>  	if (sysfs__read_int(file, (int *) &cache->level))
>  		return -1;
>  
> +	scnprintf(file, PATH_MAX, "%s/id", path);
> +	if (sysfs__read_int(file, (int *) &cache->id))
> +		return -1;
> +
>  	scnprintf(file, PATH_MAX, "%s/coherency_line_size", path);
>  	if (sysfs__read_int(file, (int *) &cache->line_size))
>  		return -1;
> -- 
> 2.34.1
> 

-- 

- Arnaldo