linux-kernel - Re: [PATCH v5 07/13] perf stat: Use affinity for closing file descriptors

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Message-ID: <20191111133052.GE12923@krava>
Date:   Mon, 11 Nov 2019 14:30:52 +0100
From:   Jiri Olsa <jolsa@...hat.com>
To:     Andi Kleen <andi@...stfloor.org>
Cc:     jolsa@...nel.org, acme@...nel.org, linux-kernel@...r.kernel.org,
        Andi Kleen <ak@...ux.intel.com>
Subject: Re: [PATCH v5 07/13] perf stat: Use affinity for closing file
 descriptors

On Thu, Nov 07, 2019 at 10:16:40AM -0800, Andi Kleen wrote:
> From: Andi Kleen <ak@...ux.intel.com>
> 
> Closing a perf fd can also trigger an IPI to the target CPU.
> Use the same affinity technique as we use for reading/enabling events
> to closing to optimize the CPU transitions.
> 
> Before on a large test case with 94 CPUs:
> 
> % time     seconds  usecs/call     calls    errors syscall
> ------ ----------- ----------- --------- --------- ----------------
>  32.56    3.085463          50     61483           close
> 
> After:
> 
>  10.54    0.735704          11     61485           close
> 
> Signed-off-by: Andi Kleen <ak@...ux.intel.com>
> 
> ---
> 
> v2: Use new iterator macros
> v3: Use new iterator macros
> Add missing affinity__cleanup
> v4:
> Update iterators again
> ---
>  tools/perf/util/evlist.c | 27 +++++++++++++++++++++++++--
>  1 file changed, 25 insertions(+), 2 deletions(-)
> 
> diff --git a/tools/perf/util/evlist.c b/tools/perf/util/evlist.c
> index dae6e846b2f8..0dcea66329e2 100644
> --- a/tools/perf/util/evlist.c
> +++ b/tools/perf/util/evlist.c
> @@ -18,6 +18,7 @@
>  #include "debug.h"
>  #include "units.h"
>  #include <internal/lib.h> // page_size
> +#include "affinity.h"
>  #include "../perf.h"
>  #include "asm/bug.h"
>  #include "bpf-event.h"
> @@ -1169,9 +1170,31 @@ void perf_evlist__set_selected(struct evlist *evlist,
>  void evlist__close(struct evlist *evlist)
>  {
>  	struct evsel *evsel;
> +	struct affinity affinity;
> +	int cpu, i;
>  
> -	evlist__for_each_entry_reverse(evlist, evsel)
> -		evsel__close(evsel);
> +	if (!evlist->core.cpus) {

should this be evlist->all_cpus?

jirka

> +		evlist__for_each_entry_reverse(evlist, evsel)
> +			evsel__close(evsel);
> +		return;
> +	}
> +
> +	if (affinity__setup(&affinity) < 0)
> +		return;
> +	evlist__for_each_cpu (evlist, i, cpu) {
> +		affinity__set(&affinity, cpu);
> +
> +		evlist__for_each_entry_reverse(evlist, evsel) {
> +			if (evsel__cpu_iter_skip(evsel, cpu))
> +			    continue;
> +			perf_evsel__close_cpu(&evsel->core, evsel->cpu_iter - 1);
> +		}
> +	}
> +	affinity__cleanup(&affinity);
> +	evlist__for_each_entry_reverse(evlist, evsel) {
> +		perf_evsel__free_fd(&evsel->core);
> +		perf_evsel__free_id(&evsel->core);
> +	}
>  }
>  
>  static int perf_evlist__create_syswide_maps(struct evlist *evlist)
> -- 
> 2.23.0
>