Re: [PATCH] perf stat: Fix wrong skipping for per-die aggregation

From: Jiri Olsa
Date: Wed Dec 23 2020 - 17:39:19 EST

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@lkp-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@lkp-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@xxxxxxxxx>
> Signed-off-by: Jin Yao <yao.jin@xxxxxxxxxxxxxxx>
> ---
> 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@xxxxxxx/

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
>