perf tools: Add time out to force stop proc map processing

System wide sampling like 'perf top' or 'perf record -a' read all
threads /proc/xxx/maps before sampling. If there are any threads which
generating a keeping growing huge maps, perf will do infinite loop
during synthesizing. Nothing will be sampled.

This patch fixes this issue by adding per-thread timeout to force stop
this kind of endless proc map processing.

PERF_RECORD_MISC_PROC_MAP_PARSE_TIME_OUT is introduced to indicate that
the mmap record are truncated by time out. User will get warning
notification when truncated mmap records are detected.

Reported-by: Ying Huang <ying.huang@intel.com>
Signed-off-by: Kan Liang <kan.liang@intel.com>
Cc: Andi Kleen <andi@firstfloor.org>
Cc: David Ahern <dsahern@gmail.com>
Cc: Ying Huang <ying.huang@intel.com>
Link: http://lkml.kernel.org/r/1434549071-25611-1-git-send-email-kan.liang@intel.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

diff --git a/include/uapi/linux/perf_event.h b/include/uapi/linux/perf_event.h
index 613ed9a..d97f84c 100644 (file)
--- a/include/uapi/linux/perf_event.h
+++ b/include/uapi/linux/perf_event.h
@@ -565,6 +565,10 @@ struct perf_event_mmap_page {
 #define PERF_RECORD_MISC_GUEST_KERNEL          (4 << 0)
 #define PERF_RECORD_MISC_GUEST_USER            (5 << 0)
 
+/*
+ * Indicates that /proc/PID/maps parsing are truncated by time out.
+ */
+#define PERF_RECORD_MISC_PROC_MAP_PARSE_TIMEOUT        (1 << 12)
 /*
  * PERF_RECORD_MISC_MMAP_DATA and PERF_RECORD_MISC_COMM_EXEC are used on
  * different events so can reuse the same bit position.

diff --git a/tools/perf/util/event.c b/tools/perf/util/event.c
index 793b150..416ba80 100644 (file)
--- a/tools/perf/util/event.c
+++ b/tools/perf/util/event.c
@@ -213,6 +213,8 @@ static int perf_event__synthesize_fork(struct perf_tool *tool,
        return 0;
 }
 
+#define PROC_MAP_PARSE_TIMEOUT (500 * 1000000ULL)
+
 int perf_event__synthesize_mmap_events(struct perf_tool *tool,
                                       union perf_event *event,
                                       pid_t pid, pid_t tgid,
@@ -222,6 +224,8 @@ int perf_event__synthesize_mmap_events(struct perf_tool *tool,
 {
        char filename[PATH_MAX];
        FILE *fp;
+       unsigned long long t;
+       bool truncation = false;
        int rc = 0;
 
        if (machine__is_default_guest(machine))
@@ -240,6 +244,7 @@ int perf_event__synthesize_mmap_events(struct perf_tool *tool,
        }
 
        event->header.type = PERF_RECORD_MMAP2;
+       t = rdclock();
 
        while (1) {
                char bf[BUFSIZ];
@@ -253,6 +258,12 @@ int perf_event__synthesize_mmap_events(struct perf_tool *tool,
                if (fgets(bf, sizeof(bf), fp) == NULL)
                        break;
 
+               if ((rdclock() - t) > PROC_MAP_PARSE_TIMEOUT) {
+                       pr_warning("Reading %s time out.\n", filename);
+                       truncation = true;
+                       goto out;
+               }
+
                /* ensure null termination since stack will be reused. */
                strcpy(execname, "");
 
@@ -301,6 +312,10 @@ int perf_event__synthesize_mmap_events(struct perf_tool *tool,
                        event->header.misc |= PERF_RECORD_MISC_MMAP_DATA;
                }
 
+out:
+               if (truncation)
+                       event->header.misc |= PERF_RECORD_MISC_PROC_MAP_PARSE_TIMEOUT;
+
                if (!strcmp(execname, ""))
                        strcpy(execname, anonstr);
 
@@ -319,6 +334,9 @@ int perf_event__synthesize_mmap_events(struct perf_tool *tool,
                        rc = -1;
                        break;
                }
+
+               if (truncation)
+                       break;
        }
 
        fclose(fp);

diff --git a/tools/perf/util/event.h b/tools/perf/util/event.h
index 5dc51ad..39868f5 100644 (file)
--- a/tools/perf/util/event.h
+++ b/tools/perf/util/event.h
@@ -265,6 +265,7 @@ struct events_stats {
        u32 nr_unknown_id;
        u32 nr_unprocessable_samples;
        u32 nr_auxtrace_errors[PERF_AUXTRACE_ERROR_MAX];
+       u32 nr_proc_map_timeout;
 };
 
 struct attr_event {

diff --git a/tools/perf/util/session.c b/tools/perf/util/session.c
index c371336..2d882fd 100644 (file)
--- a/tools/perf/util/session.c
+++ b/tools/perf/util/session.c
@@ -1064,6 +1064,8 @@ static int machines__deliver_event(struct machines *machines,
        case PERF_RECORD_MMAP:
                return tool->mmap(tool, event, sample, machine);
        case PERF_RECORD_MMAP2:
+               if (event->header.misc & PERF_RECORD_MISC_PROC_MAP_PARSE_TIMEOUT)
+                       ++evlist->stats.nr_proc_map_timeout;
                return tool->mmap2(tool, event, sample, machine);
        case PERF_RECORD_COMM:
                return tool->comm(tool, event, sample, machine);
@@ -1360,6 +1362,15 @@ static void perf_session__warn_about_errors(const struct perf_session *session)
                ui__warning("%u out of order events recorded.\n", oe->nr_unordered_events);
 
        events_stats__auxtrace_error_warn(stats);
+
+       if (stats->nr_proc_map_timeout != 0) {
+               ui__warning("%d map information files for pre-existing threads were\n"
+                           "not processed, if there are samples for addresses they\n"
+                           "will not be resolved, you may find out which are these\n"
+                           "threads by running with -v and redirecting the output\n"
+                           "to a file.\n",
+                           stats->nr_proc_map_timeout);
+       }
 }
 
 static int perf_session__flush_thread_stack(struct thread *thread,