linux-kernel - Re: [PATCH v6 04/10] libperf: Add evsel mmap support

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Message-ID: <YEtzl5c1m7jxWkEw@krava>
Date:   Fri, 12 Mar 2021 14:58:47 +0100
From:   Jiri Olsa <jolsa@...hat.com>
To:     Rob Herring <robh@...nel.org>
Cc:     Will Deacon <will@...nel.org>,
        Catalin Marinas <catalin.marinas@....com>,
        Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...hat.com>,
        Arnaldo Carvalho de Melo <acme@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Ian Rogers <irogers@...gle.com>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        honnappa.nagarahalli@....com, Zachary.Leaf@....com,
        Raphael Gault <raphael.gault@....com>,
        Jonathan Cameron <Jonathan.Cameron@...wei.com>,
        Namhyung Kim <namhyung@...nel.org>,
        Itaru Kitayama <itaru.kitayama@...il.com>,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v6 04/10] libperf: Add evsel mmap support

On Wed, Mar 10, 2021 at 05:08:31PM -0700, Rob Herring wrote:

SNIP

> +
>  static int
>  sys_perf_event_open(struct perf_event_attr *attr,
>  		    pid_t pid, int cpu, int group_fd,
> @@ -137,6 +147,8 @@ void perf_evsel__free_fd(struct perf_evsel *evsel)
>  {
>  	xyarray__delete(evsel->fd);
>  	evsel->fd = NULL;
> +	xyarray__delete(evsel->mmap);
> +	evsel->mmap = NULL;
>  }
>  
>  void perf_evsel__close(struct perf_evsel *evsel)
> @@ -156,6 +168,45 @@ void perf_evsel__close_cpu(struct perf_evsel *evsel, int cpu)
>  	perf_evsel__close_fd_cpu(evsel, cpu);
>  }
>  
> +int perf_evsel__mmap(struct perf_evsel *evsel, int pages)
> +{
> +	int ret, cpu, thread;
> +	struct perf_mmap_param mp = {
> +		.prot = PROT_READ | PROT_WRITE,
> +		.mask = (pages * page_size) - 1,
> +	};

I don't mind using evsel->fd for dimensions below,
but we need to check in here that it's defined,
that perf_evsel__open was called

jirka

> +
> +	if (evsel->mmap == NULL &&
> +	    perf_evsel__alloc_mmap(evsel, xyarray__max_x(evsel->fd), xyarray__max_y(evsel->fd)) < 0)
> +		return -ENOMEM;
> +
> +	for (cpu = 0; cpu < xyarray__max_x(evsel->fd); cpu++) {
> +		for (thread = 0; thread < xyarray__max_y(evsel->fd); thread++) {
> +			int fd = FD(evsel, cpu, thread);
> +			struct perf_mmap *map = MMAP(evsel, cpu, thread);
> +
> +			if (fd < 0)
> +				continue;
> +
> +			perf_mmap__init(map, NULL, false, NULL);
> +
> +			ret = perf_mmap__mmap(map, &mp, fd, cpu);
> +			if (ret)
> +				return -1;
> +		}
> +	}
> +
> +	return 0;
> +}
> +

SNIP