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Date:   Thu, 24 Dec 2020 09:24:49 +0800
From:   "Jin, Yao" <yao.jin@...ux.intel.com>
To:     Jiri Olsa <jolsa@...hat.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 12/24/2020 6:35 AM, Jiri Olsa wrote:
> 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/
> 

James is using "struct cpu_aggr_map" to replace "struct perf_cpu_map", but do we also need to 
replace the "struct perf_cpu_map" in "struct perf_evsel"? Otherwise the evsel->cpus will be 
inconsistent, right?

struct perf_evsel {
	...
	struct perf_cpu_map	*cpus;
	struct perf_cpu_map	*own_cpus;
	...
};

> I think we should fix that in here as well

Yes, we need to fix that in check_per_pkg() as well. As I said above, in check_per_pkg(),

struct perf_cpu_map *cpus = evsel__cpus(counter);

we should use "struct cpu_aggr_map" here.

> maybe just use hashmap (socket,die) -> bool ?
> 

Yes, hashmap should be better, saving more memory.

Thanks
Jin Yao

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

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