[ovs-dev] [PATCH 1/3] timeval: Take a backtrace on each SIGALRM.
Ethan Jackson
ethan at nicira.com
Wed Oct 24 20:49:07 UTC 2012
With this patch, timeval will take a backtrace with each SIGALRM
allowing it to retrieve a profiling snapshot instantly. This will
be useful in future patches when backtraces are logged.
Signed-off-by: Ethan Jackson <ethan at nicira.com>
---
lib/timeval.c | 68 ++++++++++++++++++++++-----------------------------------
1 file changed, 26 insertions(+), 42 deletions(-)
diff --git a/lib/timeval.c b/lib/timeval.c
index 9029faa..e507140 100644
--- a/lib/timeval.c
+++ b/lib/timeval.c
@@ -75,9 +75,8 @@ struct trace {
};
#define MAX_TRACES 50
-static struct unixctl_conn *backtrace_conn = NULL;
-static struct trace *traces = NULL;
-static size_t n_traces = 0;
+static struct trace traces[MAX_TRACES];
+static size_t trace_head = 0;
static void set_up_timer(void);
static void set_up_signal(int flags);
@@ -91,7 +90,6 @@ static struct rusage *get_recent_rusage(void);
static void refresh_rusage(void);
static void timespec_add(struct timespec *sum,
const struct timespec *a, const struct timespec *b);
-static void trace_run(void);
static unixctl_cb_func backtrace_cb;
/* Initializes the timetracking module, if not already initialized. */
@@ -100,16 +98,13 @@ time_init(void)
{
static bool inited;
- /* The best place to do this is probably a timeval_run() function.
- * However, none exists and this function is usually so fast that doing it
- * here seems fine for now. */
- trace_run();
-
if (inited) {
return;
}
inited = true;
+ memset(traces, 0, sizeof traces);
+
if (HAVE_EXECINFO_H && CACHE_TIME) {
unixctl_command_register("backtrace", "", 0, 0, backtrace_cb, NULL);
}
@@ -377,7 +372,7 @@ time_poll(struct pollfd *pollfds, int n_pollfds, long long int timeout_when,
break;
}
- if (!blocked && CACHE_TIME && !backtrace_conn) {
+ if (!blocked && CACHE_TIME) {
block_sigalrm(&oldsigs);
blocked = true;
}
@@ -398,10 +393,12 @@ sigalrm_handler(int sig_nr OVS_UNUSED)
monotonic_tick = true;
#if HAVE_EXECINFO_H
- if (backtrace_conn && n_traces < MAX_TRACES) {
- struct trace *trace = &traces[n_traces++];
+ if (CACHE_TIME) {
+ struct trace *trace = &traces[trace_head];
+
trace->n_frames = backtrace(trace->backtrace,
ARRAY_SIZE(trace->backtrace));
+ trace_head = (trace_head + 1) % MAX_TRACES;
}
#endif
}
@@ -581,42 +578,38 @@ get_cpu_usage(void)
}
static void
-trace_run(void)
+format_backtraces(struct ds *ds)
{
+ time_init();
+
#if HAVE_EXECINFO_H
- if (backtrace_conn && n_traces >= MAX_TRACES) {
- struct unixctl_conn *reply_conn = backtrace_conn;
- struct ds ds = DS_EMPTY_INITIALIZER;
+ if (CACHE_TIME) {
sigset_t oldsigs;
size_t i;
block_sigalrm(&oldsigs);
- for (i = 0; i < n_traces; i++) {
+ for (i = 0; i < MAX_TRACES; i++) {
struct trace *trace = &traces[i];
char **frame_strs;
size_t j;
+ if (!trace->n_frames) {
+ continue;
+ }
+
frame_strs = backtrace_symbols(trace->backtrace, trace->n_frames);
- ds_put_format(&ds, "Backtrace %zu\n", i + 1);
+ ds_put_format(ds, "Backtrace %zu\n", i + 1);
for (j = 0; j < trace->n_frames; j++) {
- ds_put_format(&ds, "%s\n", frame_strs[j]);
+ ds_put_format(ds, "%s\n", frame_strs[j]);
}
- ds_put_cstr(&ds, "\n");
+ ds_put_cstr(ds, "\n");
free(frame_strs);
}
-
- free(traces);
- traces = NULL;
- n_traces = 0;
- backtrace_conn = NULL;
-
+ ds_chomp(ds, '\n');
unblock_sigalrm(&oldsigs);
-
- unixctl_command_reply(reply_conn, ds_cstr(&ds));
- ds_destroy(&ds);
}
#endif
}
@@ -664,21 +657,12 @@ backtrace_cb(struct unixctl_conn *conn,
int argc OVS_UNUSED, const char *argv[] OVS_UNUSED,
void *aux OVS_UNUSED)
{
- sigset_t oldsigs;
+ struct ds ds = DS_EMPTY_INITIALIZER;
assert(HAVE_EXECINFO_H && CACHE_TIME);
-
- if (backtrace_conn) {
- unixctl_command_reply_error(conn, "In Use");
- return;
- }
- assert(!traces);
-
- block_sigalrm(&oldsigs);
- backtrace_conn = conn;
- traces = xmalloc(MAX_TRACES * sizeof *traces);
- n_traces = 0;
- unblock_sigalrm(&oldsigs);
+ format_backtraces(&ds);
+ unixctl_command_reply(conn, ds_cstr(&ds));
+ ds_destroy(&ds);
}
void
--
1.7.9.5
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