linux-kernel - Re: [PATCH v4 04/16] perf kvm: Use subtraction for comparison metrics

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Date:   Mon, 13 Mar 2023 14:58:22 -0300
From:   Arnaldo Carvalho de Melo <acme@...nel.org>
To:     Leo Yan <leo.yan@...aro.org>
Cc:     Jiri Olsa <jolsa@...nel.org>, Namhyung Kim <namhyung@...nel.org>,
        Ian Rogers <irogers@...gle.com>,
        John Garry <john.g.garry@...cle.com>,
        James Clark <james.clark@....com>,
        Adrian Hunter <adrian.hunter@...el.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...hat.com>,
        Mark Rutland <mark.rutland@....com>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        linux-perf-users@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH v4 04/16] perf kvm: Use subtraction for comparison metrics

Em Mon, Mar 13, 2023 at 07:40:06PM +0800, Leo Yan escreveu:
> Currently the metrics comparison uses greater operator (>), it returns
> the boolean value (0 or 1).
> 
> This patch changes to use subtraction as comparison result, which can
> be used by histograms sorting.  Since the subtraction result is u64
> type, we change the function return type from int to int64_t to avoid
> overflow.

Not building at his point in the series:

  LD      /tmp/build/perf-tools-next/util/perf-in.o
builtin-kvm.c:80:18: error: initialization of ‘int (*)(struct kvm_event *, struct kvm_event *, int)’ from incompatible pointer type ‘int64_t (*)(struct kvm_event *, struct kvm_event *, int)’ {aka ‘long int (*)(struct kvm_event *, struct kvm_event *, int)’} [-Werror=incompatible-pointer-types]
   80 |         { #name, cmp_event_ ## compare_key }
      |                  ^~~~~~~~~~
builtin-kvm.c:83:9: note: in expansion of macro ‘DEF_SORT_NAME_KEY’
   83 |         DEF_SORT_NAME_KEY(sample, count),
      |         ^~~~~~~~~~~~~~~~~
builtin-kvm.c:80:18: note: (near initialization for ‘keys[0].key’)
   80 |         { #name, cmp_event_ ## compare_key }
      |                  ^~~~~~~~~~
builtin-kvm.c:83:9: note: in expansion of macro ‘DEF_SORT_NAME_KEY’
   83 |         DEF_SORT_NAME_KEY(sample, count),
      |         ^~~~~~~~~~~~~~~~~
builtin-kvm.c:80:18: error: initialization of ‘int (*)(struct kvm_event *, struct kvm_event *, int)’ from incompatible pointer type ‘int64_t (*)(struct kvm_event *, struct kvm_event *, int)’ {aka ‘long int (*)(struct kvm_event *, struct kvm_event *, int)’} [-Werror=incompatible-pointer-types]
   80 |         { #name, cmp_event_ ## compare_key }
      |                  ^~~~~~~~~~
builtin-kvm.c:84:9: note: in expansion of macro ‘DEF_SORT_NAME_KEY’
   84 |         DEF_SORT_NAME_KEY(time, mean),
      |         ^~~~~~~~~~~~~~~~~
builtin-kvm.c:80:18: note: (near initialization for ‘keys[1].key’)
   80 |         { #name, cmp_event_ ## compare_key }
      |                  ^~~~~~~~~~
builtin-kvm.c:84:9: note: in expansion of macro ‘DEF_SORT_NAME_KEY’
   84 |         DEF_SORT_NAME_KEY(time, mean),
      |         ^~~~~~~~~~~~~~~~~
cc1: all warnings being treated as errors
make[3]: *** [/var/home/acme/git/perf-tools-next/tools/build/Makefile.build:97: /tmp/build/perf-tools-next/builtin-kvm.o] Error 1
make[3]: *** Waiting for unfinished jobs....
make[2]: *** [Makefile.perf:673: /tmp/build/perf-tools-next/perf-in.o] Error 2
make[2]: *** Waiting for unfinished jobs....
  CC      /tmp/build/perf-tools-next/pmu-events/pmu-events.o
  LD      /tmp/build/perf-tools-next/pmu-events/pmu-events-in.o
make[1]: *** [Makefile.perf:236: sub-make] Error 2
make: *** [Makefile:113: install-bin] Error 2
make: Leaving directory '/var/home/acme/git/perf-tools-next/tools/perf'

 Performance counter stats for 'make -k BUILD_BPF_SKEL=1 CORESIGHT=1 O=/tmp/build/perf-tools-next -C tools/perf install-bin':

       46519453561      cycles:u
       73484239007      instructions:u                   #    1.58  insn per cycle

      10.053592077 seconds time elapsed

      10.925077000 seconds user
       8.045887000 seconds sys


⬢[acme@...lbox perf-tools-next]$ git log --oneline -4
40843f667620dcf3 (HEAD) perf kvm: Use subtraction for comparison metrics
c6a5a089864171f2 perf kvm: Move up metrics helpers
1d75bc17ffc933aa perf kvm: Add pointer to 'perf_kvm_stat' in kvm event
4568393639938020 perf kvm: Refactor overall statistics
⬢[acme@...lbox perf-tools-next]$

⬢[acme@...lbox perf-tools-next]$ gcc --version
gcc (GCC) 12.2.1 20221121 (Red Hat 12.2.1-4)
 
> Signed-off-by: Leo Yan <leo.yan@...aro.org>
> ---
>  tools/perf/builtin-kvm.c | 6 +++---
>  1 file changed, 3 insertions(+), 3 deletions(-)
> 
> diff --git a/tools/perf/builtin-kvm.c b/tools/perf/builtin-kvm.c
> index 62c097a37da9..4e9519390da6 100644
> --- a/tools/perf/builtin-kvm.c
> +++ b/tools/perf/builtin-kvm.c
> @@ -63,10 +63,10 @@ static u64 get_event_ ##func(struct kvm_event *event, int vcpu)		\
>  
>  #define COMPARE_EVENT_KEY(func, field)					\
>  GET_EVENT_KEY(func, field)						\
> -static int cmp_event_ ## func(struct kvm_event *one,			\
> +static int64_t cmp_event_ ## func(struct kvm_event *one,		\
>  			      struct kvm_event *two, int vcpu)		\
>  {									\
> -	return get_event_ ##func(one, vcpu) >				\
> +	return get_event_ ##func(one, vcpu) -				\
>  	       get_event_ ##func(two, vcpu);				\
>  }
>  
> @@ -523,7 +523,7 @@ static void insert_to_result(struct rb_root *result, struct kvm_event *event,
>  		p = container_of(*rb, struct kvm_event, rb);
>  		parent = *rb;
>  
> -		if (bigger(event, p, vcpu))
> +		if (bigger(event, p, vcpu) > 0)
>  			rb = &(*rb)->rb_left;
>  		else
>  			rb = &(*rb)->rb_right;
> -- 
> 2.34.1
> 

-- 

- Arnaldo