From d9cf837ef9629ab34167bd6fc0141383ddb8813a Mon Sep 17 00:00:00 2001 From: Corey Ashford Date: Fri, 19 Nov 2010 17:37:24 -0800 Subject: [PATCH] perf stat: Change and clean up sys_perf_event_open error handling This patch makes several changes to "perf stat": - "perf stat" will no longer go ahead and run the application when one or more of the specified events could not be opened. - Use error() and die() instead of pr_err() so that the output is more consistent with "perf top" and "perf record". - Handle permission errors in a more robust way, and in a similar way to "perf record" and "perf top". In addition, the sys_perf_event_open() error handling of "perf top" and "perf record" is made more consistent and adds the following phrase when an event doesn't open (with something ther than an access or permission error): "/bin/dmesg may provide additional information." This is added because kernel code doesn't have a good way of expressing detailed errors to user space, so its only avenue is to use printk's. However, many users may not think of looking at dmesg to find out why an event is being rejected. Cc: Frederic Weisbecker Cc: Ingo Molnar Cc: Peter Zijlstra Cc: Ian Munsie Cc: Michael Ellerman LKML-Reference: <1290217044-26293-1-git-send-email-cjashfor@linux.vnet.ibm.com> Signed-off-by: Corey Ashford Signed-off-by: Arnaldo Carvalho de Melo --- tools/perf/builtin-record.c | 2 +- tools/perf/builtin-stat.c | 38 +++++++++++++++++++++++-------------- tools/perf/builtin-top.c | 6 ++++-- 3 files changed, 29 insertions(+), 17 deletions(-) diff --git a/tools/perf/builtin-record.c b/tools/perf/builtin-record.c index 93bd2ff001fb..d9dd47885218 100644 --- a/tools/perf/builtin-record.c +++ b/tools/perf/builtin-record.c @@ -326,7 +326,7 @@ try_again: goto try_again; } printf("\n"); - error("perfcounter syscall returned with %d (%s)\n", + error("sys_perf_event_open() syscall returned with %d (%s). /bin/dmesg may provide additional information.\n", fd[nr_cpu][counter][thread_index], strerror(err)); #if defined(__i386__) || defined(__x86_64__) diff --git a/tools/perf/builtin-stat.c b/tools/perf/builtin-stat.c index b3e568ffad27..970a7f2a083d 100644 --- a/tools/perf/builtin-stat.c +++ b/tools/perf/builtin-stat.c @@ -153,9 +153,9 @@ struct stats walltime_nsecs_stats; attrs[counter].config == PERF_COUNT_##c) #define ERR_PERF_OPEN \ -"Error: counter %d, sys_perf_event_open() syscall returned with %d (%s)\n" +"counter %d, sys_perf_event_open() syscall returned with %d (%s). /bin/dmesg may provide additional information." -static int create_perf_stat_counter(int counter) +static int create_perf_stat_counter(int counter, bool *perm_err) { struct perf_event_attr *attr = attrs + counter; int thread; @@ -171,11 +171,14 @@ static int create_perf_stat_counter(int counter) for (cpu = 0; cpu < nr_cpus; cpu++) { fd[cpu][counter][0] = sys_perf_event_open(attr, -1, cpumap[cpu], -1, 0); - if (fd[cpu][counter][0] < 0) - pr_debug(ERR_PERF_OPEN, counter, + if (fd[cpu][counter][0] < 0) { + if (errno == EPERM || errno == EACCES) + *perm_err = true; + error(ERR_PERF_OPEN, counter, fd[cpu][counter][0], strerror(errno)); - else + } else { ++ncreated; + } } } else { attr->inherit = !no_inherit; @@ -186,12 +189,15 @@ static int create_perf_stat_counter(int counter) for (thread = 0; thread < thread_num; thread++) { fd[0][counter][thread] = sys_perf_event_open(attr, all_tids[thread], -1, -1, 0); - if (fd[0][counter][thread] < 0) - pr_debug(ERR_PERF_OPEN, counter, + if (fd[0][counter][thread] < 0) { + if (errno == EPERM || errno == EACCES) + *perm_err = true; + error(ERR_PERF_OPEN, counter, fd[0][counter][thread], strerror(errno)); - else + } else { ++ncreated; + } } } @@ -332,6 +338,7 @@ static int run_perf_stat(int argc __used, const char **argv) int status = 0; int counter, ncreated = 0; int child_ready_pipe[2], go_pipe[2]; + bool perm_err = false; const bool forks = (argc > 0); char buf; @@ -390,12 +397,15 @@ static int run_perf_stat(int argc __used, const char **argv) } for (counter = 0; counter < nr_counters; counter++) - ncreated += create_perf_stat_counter(counter); - - if (ncreated == 0) { - pr_err("No permission to collect %sstats.\n" - "Consider tweaking /proc/sys/kernel/perf_event_paranoid.\n", - system_wide ? "system-wide " : ""); + ncreated += create_perf_stat_counter(counter, &perm_err); + + if (ncreated < nr_counters) { + if (perm_err) + error("You may not have permission to collect %sstats.\n" + "\t Consider tweaking" + " /proc/sys/kernel/perf_event_paranoid or running as root.", + system_wide ? "system-wide " : ""); + die("Not all events could be opened.\n"); if (child_pid != -1) kill(child_pid, SIGTERM); return -1; diff --git a/tools/perf/builtin-top.c b/tools/perf/builtin-top.c index dd625808c2a5..3d2b47d5121a 100644 --- a/tools/perf/builtin-top.c +++ b/tools/perf/builtin-top.c @@ -1214,7 +1214,9 @@ try_again: int err = errno; if (err == EPERM || err == EACCES) - die("No permission - are you root?\n"); + die("Permission error - are you root?\n" + "\t Consider tweaking" + " /proc/sys/kernel/perf_event_paranoid.\n"); /* * If it's cycles then fall back to hrtimer * based cpu-clock-tick sw counter, which @@ -1231,7 +1233,7 @@ try_again: goto try_again; } printf("\n"); - error("perfcounter syscall returned with %d (%s)\n", + error("sys_perf_event_open() syscall returned with %d (%s). /bin/dmesg may provide additional information.\n", fd[i][counter][thread_index], strerror(err)); die("No CONFIG_PERF_EVENTS=y kernel support configured?\n"); exit(-1); -- 2.39.2