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Date:   Wed, 23 Dec 2020 23:35:45 +0100
From:   Jiri Olsa <jolsa@...hat.com>
To:     Jin Yao <yao.jin@...ux.intel.com>
Cc:     acme@...nel.org, jolsa@...nel.org, peterz@...radead.org,
        mingo@...hat.com, alexander.shishkin@...ux.intel.com,
        Linux-kernel@...r.kernel.org, ak@...ux.intel.com,
        kan.liang@...el.com, yao.jin@...el.com,
        James Clark <james.clark@....com>
Subject: Re: [PATCH] perf stat: Fix wrong skipping for per-die aggregation

On Wed, Dec 16, 2020 at 03:01:46PM +0800, Jin Yao wrote:
> Uncore becomes die-scope on Xeon Cascade Lake-AP and perf has supported
> --per-die aggregation yet.
> 
> One issue is found in check_per_pkg() for uncore events running on
> AP system. On cascade Lake-AP, we have:
> 
> S0-D0
> S0-D1
> S1-D0
> S1-D1
> 
> But in check_per_pkg(), S0-D1 and S1-D1 are skipped because the
> mask bits for S0 and S1 have been set for S0-D0 and S1-D0. It doesn't
> check die_id. So the counting for S0-D1 and S1-D1 are set to zero.
> That's not correct.
> 
> root@...-csl-2ap4 ~# ./perf stat -a -I 1000 -e llc_misses.mem_read --per-die -- sleep 5
>      1.001460963 S0-D0           1            1317376 Bytes llc_misses.mem_read
>      1.001460963 S0-D1           1             998016 Bytes llc_misses.mem_read
>      1.001460963 S1-D0           1             970496 Bytes llc_misses.mem_read
>      1.001460963 S1-D1           1            1291264 Bytes llc_misses.mem_read
>      2.003488021 S0-D0           1            1082048 Bytes llc_misses.mem_read
>      2.003488021 S0-D1           1            1919040 Bytes llc_misses.mem_read
>      2.003488021 S1-D0           1             890752 Bytes llc_misses.mem_read
>      2.003488021 S1-D1           1            2380800 Bytes llc_misses.mem_read
>      3.005613270 S0-D0           1            1126080 Bytes llc_misses.mem_read
>      3.005613270 S0-D1           1            2898176 Bytes llc_misses.mem_read
>      3.005613270 S1-D0           1             870912 Bytes llc_misses.mem_read
>      3.005613270 S1-D1           1            3388608 Bytes llc_misses.mem_read
>      4.007627598 S0-D0           1            1124608 Bytes llc_misses.mem_read
>      4.007627598 S0-D1           1            3884416 Bytes llc_misses.mem_read
>      4.007627598 S1-D0           1             921088 Bytes llc_misses.mem_read
>      4.007627598 S1-D1           1            4451840 Bytes llc_misses.mem_read
>      5.001479927 S0-D0           1             963328 Bytes llc_misses.mem_read
>      5.001479927 S0-D1           1            4831936 Bytes llc_misses.mem_read
>      5.001479927 S1-D0           1             895104 Bytes llc_misses.mem_read
>      5.001479927 S1-D1           1            5496640 Bytes llc_misses.mem_read
> 
> From above output, we can see S0-D1 and S1-D1 don't report the interval
> values, they are continued to grow. That's because check_per_pkg() wrongly
> decides to use zero counts for S0-D1 and S1-D1.
> 
> So in check_per_pkg(), we should use a pair of die_id + socket_id to
> decide if this cpu counts needs to skip. Only considering socket_id is
> not enough.
> 
> Now with this patch,
> 
> root@...-csl-2ap4 ~# ./perf stat -a -I 1000 -e llc_misses.mem_read --per-die -- sleep 5
>      1.001622560 S0-D0           1            1210176 Bytes llc_misses.mem_read
>      1.001622560 S0-D1           1             950208 Bytes llc_misses.mem_read
>      1.001622560 S1-D0           1             968704 Bytes llc_misses.mem_read
>      1.001622560 S1-D1           1            1113280 Bytes llc_misses.mem_read
>      2.004399430 S0-D0           1            1258560 Bytes llc_misses.mem_read
>      2.004399430 S0-D1           1            1011008 Bytes llc_misses.mem_read
>      2.004399430 S1-D0           1            1036544 Bytes llc_misses.mem_read
>      2.004399430 S1-D1           1            1237376 Bytes llc_misses.mem_read
>      3.006535657 S0-D0           1            1036608 Bytes llc_misses.mem_read
>      3.006535657 S0-D1           1             906560 Bytes llc_misses.mem_read
>      3.006535657 S1-D0           1             994112 Bytes llc_misses.mem_read
>      3.006535657 S1-D1           1            1025472 Bytes llc_misses.mem_read
>      4.008934402 S0-D0           1            1005120 Bytes llc_misses.mem_read
>      4.008934402 S0-D1           1             882368 Bytes llc_misses.mem_read
>      4.008934402 S1-D0           1             961408 Bytes llc_misses.mem_read
>      4.008934402 S1-D1           1             988352 Bytes llc_misses.mem_read
>      5.001605406 S0-D0           1            1930240 Bytes llc_misses.mem_read
>      5.001605406 S0-D1           1            1134272 Bytes llc_misses.mem_read
>      5.001605406 S1-D0           1            1531136 Bytes llc_misses.mem_read
>      5.001605406 S1-D1           1            2230848 Bytes llc_misses.mem_read
> 
> On no-die system, die_id is 0, this patch keeps original behavior unchanged.
> 
> Reported-by: Huang Ying <ying.huang@...el.com>
> Signed-off-by: Jin Yao <yao.jin@...ux.intel.com>
> ---
>  tools/perf/util/cpumap.h |  2 ++
>  tools/perf/util/stat.c   | 21 +++++++++++++++++----
>  2 files changed, 19 insertions(+), 4 deletions(-)
> 
> diff --git a/tools/perf/util/cpumap.h b/tools/perf/util/cpumap.h
> index 3a442f021468..58604c047121 100644
> --- a/tools/perf/util/cpumap.h
> +++ b/tools/perf/util/cpumap.h
> @@ -7,6 +7,8 @@
>  #include <internal/cpumap.h>
>  #include <perf/cpumap.h>
>  
> +#define CPU_MAP_MAX_DIE	256
> +
>  struct perf_record_cpu_map_data;
>  
>  struct perf_cpu_map *perf_cpu_map__empty_new(int nr);
> diff --git a/tools/perf/util/stat.c b/tools/perf/util/stat.c
> index 1e125e39ff84..b3fc6e261fe0 100644
> --- a/tools/perf/util/stat.c
> +++ b/tools/perf/util/stat.c
> @@ -282,9 +282,9 @@ static void zero_per_pkg(struct evsel *counter)
>  static int check_per_pkg(struct evsel *counter,
>  			 struct perf_counts_values *vals, int cpu, bool *skip)
>  {
> -	unsigned long *mask = counter->per_pkg_mask;
> +	unsigned long *mask = counter->per_pkg_mask, *l;
>  	struct perf_cpu_map *cpus = evsel__cpus(counter);
> -	int s;
> +	int s, d;
>  
>  	*skip = false;
>  
> @@ -295,7 +295,7 @@ static int check_per_pkg(struct evsel *counter,
>  		return 0;
>  
>  	if (!mask) {
> -		mask = zalloc(cpu__max_cpu());
> +		mask = zalloc(cpu__max_cpu() * CPU_MAP_MAX_DIE);
>  		if (!mask)
>  			return -ENOMEM;
>  
> @@ -317,7 +317,20 @@ static int check_per_pkg(struct evsel *counter,
>  	if (s < 0)
>  		return -1;
>  
> -	*skip = test_and_set_bit(s, mask) == 1;
> +	d = cpu_map__get_die(cpus, cpu, NULL);
> +	if (d < 0)
> +		return -1;
> +
> +	/*
> +	 * On multi-die system, die_id < 256. We use a pair
> +	 * of socket + die to identify the used bit.
> +	 * On no-die system, die_id is 0, l = &mask[0]. It doesn't
> +	 * change original "test_and_set_bit(s, mask)" behavior.
> +	 */
> +	d &= 0xff;
> +	l = &mask[d];

James is fixing the aggregation, because we could get large socket numbers:
  https://lore.kernel.org/lkml/20201126141328.6509-1-james.clark@arm.com/

I think we should fix that in here as well
maybe just use hashmap (socket,die) -> bool ?

jirka

> +
> +	*skip = test_and_set_bit(s, l) == 1;
>  	return 0;
>  }
>  
> -- 
> 2.17.1
> 

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