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    Subject[tip:perf/core] perf mem record: Check for memory events support
    Commit-ID:  54fbad54ebcde9db9c7459e9e379f2350c25e1f1
    Gitweb: http://git.kernel.org/tip/54fbad54ebcde9db9c7459e9e379f2350c25e1f1
    Author: Jiri Olsa <jolsa@kernel.org>
    AuthorDate: Wed, 24 Feb 2016 09:46:42 +0100
    Committer: Arnaldo Carvalho de Melo <acme@redhat.com>
    CommitDate: Wed, 24 Feb 2016 10:10:59 -0300

    perf mem record: Check for memory events support

    Check if current kernel support available memory events and display the
    status within -e list option:

    $ perf mem record -e list
    ldlat-loads : available
    ldlat-stores : available

    Signed-off-by: Jiri Olsa <jolsa@kernel.org>
    Tested-by: Arnaldo Carvalho de Melo <acme@redhat.com>
    Cc: Andi Kleen <ak@linux.intel.com>
    Cc: David Ahern <dsahern@gmail.com>
    Cc: Namhyung Kim <namhyung@kernel.org>
    Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
    Cc: Stephane Eranian <eranian@google.com>
    Link: http://lkml.kernel.org/r/1456303616-26926-2-git-send-email-jolsa@kernel.org
    Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
    ---
    tools/perf/builtin-mem.c | 20 ++++++++++++++++----
    tools/perf/util/mem-events.c | 35 ++++++++++++++++++++++++++++++++---
    tools/perf/util/mem-events.h | 3 +++
    3 files changed, 51 insertions(+), 7 deletions(-)

    diff --git a/tools/perf/builtin-mem.c b/tools/perf/builtin-mem.c
    index b3f8a89..f1fa7b8 100644
    --- a/tools/perf/builtin-mem.c
    +++ b/tools/perf/builtin-mem.c
    @@ -40,10 +40,11 @@ static int parse_record_events(const struct option *opt,
    for (j = 0; j < PERF_MEM_EVENTS__MAX; j++) {
    struct perf_mem_event *e = &perf_mem_events[j];

    - fprintf(stderr, "%-20s%s",
    - e->tag, verbose ? "" : "\n");
    - if (verbose)
    - fprintf(stderr, " [%s]\n", e->name);
    + fprintf(stderr, "%-13s%-*s%s\n",
    + e->tag,
    + verbose ? 25 : 0,
    + verbose ? e->name : "",
    + e->supported ? ": available" : "");
    }
    exit(0);
    }
    @@ -92,6 +93,12 @@ static int __cmd_record(int argc, const char **argv, struct perf_mem *mem)
    if (!perf_mem_events[j].record)
    continue;

    + if (!perf_mem_events[j].supported) {
    + pr_err("failed: event '%s' not supported\n",
    + perf_mem_events[j].name);
    + return -1;
    + }
    +
    rec_argv[i++] = "-e";
    rec_argv[i++] = perf_mem_events[j].name;
    };
    @@ -355,6 +362,11 @@ int cmd_mem(int argc, const char **argv, const char *prefix __maybe_unused)
    NULL
    };

    + if (perf_mem_events__init()) {
    + pr_err("failed: memory events not supported\n");
    + return -1;
    + }
    +
    argc = parse_options_subcommand(argc, argv, mem_options, mem_subcommands,
    mem_usage, PARSE_OPT_STOP_AT_NON_OPTION);

    diff --git a/tools/perf/util/mem-events.c b/tools/perf/util/mem-events.c
    index b1507c0..e21853f 100644
    --- a/tools/perf/util/mem-events.c
    +++ b/tools/perf/util/mem-events.c
    @@ -2,15 +2,20 @@
    #include <stdlib.h>
    #include <string.h>
    #include <errno.h>
    +#include <sys/types.h>
    +#include <sys/stat.h>
    +#include <unistd.h>
    +#include <api/fs/fs.h>
    #include "mem-events.h"
    #include "debug.h"

    -#define E(t, n) { .tag = t, .name = n }
    +#define E(t, n, s) { .tag = t, .name = n, .sysfs_name = s }

    struct perf_mem_event perf_mem_events[PERF_MEM_EVENTS__MAX] = {
    - E("ldlat-loads", "cpu/mem-loads,ldlat=30/P"),
    - E("ldlat-stores", "cpu/mem-stores/P"),
    + E("ldlat-loads", "cpu/mem-loads,ldlat=30/P", "mem-loads"),
    + E("ldlat-stores", "cpu/mem-stores/P", "mem-stores"),
    };
    +#undef E

    #undef E

    @@ -49,3 +54,27 @@ int perf_mem_events__parse(const char *str)
    pr_err("failed: event '%s' not found, use '-e list' to get list of available events\n", str);
    return -1;
    }
    +
    +int perf_mem_events__init(void)
    +{
    + const char *mnt = sysfs__mount();
    + bool found = false;
    + int j;
    +
    + if (!mnt)
    + return -ENOENT;
    +
    + for (j = 0; j < PERF_MEM_EVENTS__MAX; j++) {
    + char path[PATH_MAX];
    + struct perf_mem_event *e = &perf_mem_events[j];
    + struct stat st;
    +
    + scnprintf(path, PATH_MAX, "%s/devices/cpu/events/%s",
    + mnt, e->sysfs_name);
    +
    + if (!stat(path, &st))
    + e->supported = found = true;
    + }
    +
    + return found ? 0 : -ENOENT;
    +}
    diff --git a/tools/perf/util/mem-events.h b/tools/perf/util/mem-events.h
    index 2995bae..75c1660 100644
    --- a/tools/perf/util/mem-events.h
    +++ b/tools/perf/util/mem-events.h
    @@ -5,8 +5,10 @@

    struct perf_mem_event {
    bool record;
    + bool supported;
    const char *tag;
    const char *name;
    + const char *sysfs_name;
    };

    enum {
    @@ -18,5 +20,6 @@ enum {
    extern struct perf_mem_event perf_mem_events[PERF_MEM_EVENTS__MAX];

    int perf_mem_events__parse(const char *str);
    +int perf_mem_events__init(void);

    #endif /* __PERF_MEM_EVENTS_H */
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