Added new logic to get multiplier and shift for converting TSC trace clock
to nanoseconds, using perf kernel interface. The new logic is used only in
host - guest tracing use case, when the user did not specify any tracing
clock and KVM time sync plugin is available. Then the x86-tsc clock is
auto selected for the current tracing session. There is one limitation -
per CPU multiplier or shift is not supported.
Signed-off-by: Tzvetomir Stoyanov (VMware) <tz.stoyanov@xxxxxxxxx>
---
tracecmd/include/trace-local.h | 7 ++
tracecmd/trace-record.c | 124 ++++++++++++++++++++++++++-------
2 files changed, 107 insertions(+), 24 deletions(-)
diff --git a/tracecmd/include/trace-local.h b/tracecmd/include/trace-local.h
index 6e39d27d..8a88ab9c 100644
--- a/tracecmd/include/trace-local.h
+++ b/tracecmd/include/trace-local.h
@@ -199,6 +199,12 @@ struct filter_pids {
int exclude;
};
+struct tsc_nsec {
+ int mult;
+ int shift;
+ int offset;
+};
+
struct buffer_instance {
struct buffer_instance *next;
char *name;
@@ -234,6 +240,7 @@ struct buffer_instance {
int get_procmap;
const char *clock;
+ struct tsc_nsec tsc2nsec;
unsigned int *client_ports;
struct trace_seq *s_save;
diff --git a/tracecmd/trace-record.c b/tracecmd/trace-record.c
index a0eb0385..117e4f17 100644
--- a/tracecmd/trace-record.c
+++ b/tracecmd/trace-record.c
@@ -57,6 +57,7 @@
#define MAX_LATENCY "tracing_max_latency"
#define STAMP "stamp"
#define FUNC_STACK_TRACE "func_stack_trace"
+#define TSC_CLOCK "x86-tsc"
enum trace_type {
TRACE_TYPE_RECORD = 1,
@@ -4104,6 +4105,7 @@ enum {
DATA_FL_NONE = 0,
DATA_FL_DATE = 1,
DATA_FL_OFFSET = 2,
+ DATA_FL_GUEST = 4,
};
static void add_options(struct tracecmd_output *handle, struct common_record_context *ctx)
@@ -5676,6 +5678,100 @@ check_instance_die(struct buffer_instance *instance, char *param)
tracefs_instance_get_name(instance->tracefs), param);
}
+static int get_tsc_nsec(int *shift, int *mult, int *offset)
+{
+ int cpus = tracecmd_count_cpus();
+ int cpu_shift, cpu_mult, cpu_offset;
+ struct trace_perf perf;
+ int ret;
+ int i;
+
+ ret = trace_perf_init(&perf, 1, 0, getpid());
+ if (!ret)
+ ret = trace_perf_open(&perf);
+ if (ret)
+ return ret;
+ cpu_shift = perf.mmap->time_shift;
+ cpu_mult = perf.mmap->time_mult;
+ /* ToDo set the offset, should we use perf.mmap->time_offset ? */
+ cpu_offset = 0;
+ for (i = 1; i < cpus; i++) {
+ trace_perf_close(&perf);
+ ret = trace_perf_init(&perf, 1, i, getpid());
+ if (!ret)
+ ret = trace_perf_open(&perf);
+ if (ret)
+ break;
+ if (perf.mmap->time_shift != cpu_shift ||
+ perf.mmap->time_mult != cpu_mult) {
+ warning("Found different TSC multiplier and shift for CPU %d: %d;%d instead of %d;%d",
+ i, perf.mmap->time_mult, perf.mmap->time_shift, cpu_mult, cpu_shift);
+ break;
+ }
+ }
+ trace_perf_close(&perf);
+ if (i < cpus)
+ return -1;
+
+ *shift = cpu_shift;
+ *mult = cpu_mult;
+ *offset = cpu_offset;
+
+ return 0;
+}
+
+static void set_vsync_clock(void)
+{
+ const char *clock = top_instance.clock;
+ struct buffer_instance *instance;
+ bool tsc2nsec = false;
+ int shift, mult, offset;
+
+ /*
+ * If no clock is specified for the top trace instance AND
+ * KVM time sync protocol is available AND
+ * TSC to nsec multiplier and shift are available:
+ * force using the x86-tsc clock for this host-guest tracing session
+ * and store TSC to nsec multiplier and shift.
+ */
+ if (!clock && tsync_proto_is_supported("kvm") &&
+ !get_tsc_nsec(&shift, &mult, &offset) && mult) {
+ top_instance.clock = strdup(TSC_CLOCK);
+ if (!top_instance.clock)
+ die("Could not allocate top instance clock");
+ clock = top_instance.clock;
+ top_instance.tsc2nsec.mult = mult;
+ top_instance.tsc2nsec.shift = shift;
+ top_instance.tsc2nsec.offset = offset;
+ tsc2nsec = true;
+ }
+
+ if (!clock && !top_instance.tsync_loop_interval)
+ return;
+ for_all_instances(instance) {
+ if (clock) {
+ /* use the same clock in all tracing peers */
+ if (is_guest(instance) &&
+ !(instance->flags & BUFFER_FL_HAS_CLOCK)) {
+ add_argv(instance,
+ (char *)top_instance.clock, true);
+ add_argv(instance, "-C", true);
+ if (!instance->clock) {
+ instance->clock = strdup((char *)top_instance.clock);
+ if (!instance->clock)
+ die("Could not allocate instance clock");
+ }
+ if (tsc2nsec) {
+ instance->tsc2nsec.mult = mult;
+ instance->tsc2nsec.shift = shift;
+ instance->tsc2nsec.offset = offset;
+ }
+ }
+ }
+ instance->tsync_loop_interval = top_instance.tsync_loop_interval;
+ }
+}
+
static void parse_record_options(int argc,
char **argv,
enum trace_cmd curr_cmd,
@@ -5691,7 +5787,6 @@ static void parse_record_options(int argc,
int name_counter = 0;
int negative = 0;
struct buffer_instance *instance, *del_list = NULL;
- bool guest_sync_set = false;
int do_children = 0;
int fpids_count = 0;
@@ -5825,6 +5920,7 @@ static void parse_record_options(int argc,
ctx->instance->port = port;
ctx->instance->name = name;
add_instance(ctx->instance, 0);
+ ctx->data_flags |= DATA_FL_GUEST;
break;
}
case 'F':
@@ -5872,8 +5968,6 @@ static void parse_record_options(int argc,
check_instance_die(ctx->instance, "-C");
ctx->instance->clock = optarg;
ctx->instance->flags |= BUFFER_FL_HAS_CLOCK;
- if (is_top_instance(ctx->instance))
- guest_sync_set = true;
break;
case 'v':
negative = 1;
@@ -6118,7 +6212,6 @@ static void parse_record_options(int argc,
case OPT_tsyncinterval:
cmd_check_die(ctx, CMD_set, *(argv+1), "--tsync-interval");
top_instance.tsync_loop_interval = atoi(optarg);
- guest_sync_set = true;
break;
case OPT_fork:
if (!IS_START(ctx))
@@ -6145,26 +6238,6 @@ static void parse_record_options(int argc,
add_argv(instance, "--date", true);
}
}
- if (guest_sync_set) {
- /* If -C is specified, prepend clock to all guest VM flags */
- for_all_instances(instance) {
- if (top_instance.clock) {
- if (is_guest(instance) &&
- !(instance->flags & BUFFER_FL_HAS_CLOCK)) {
- add_argv(instance,
- (char *)top_instance.clock,
- true);
- add_argv(instance, "-C", true);
- if (!instance->clock) {
- instance->clock = strdup((char *)top_instance.clock);
- if (!instance->clock)
- die("Could not allocate instance clock");
- }
- }
- }
- instance->tsync_loop_interval = top_instance.tsync_loop_interval;
- }
- }
if (!ctx->filtered && ctx->instance->filter_mod)
add_func(&ctx->instance->filter_funcs,
@@ -6301,6 +6374,9 @@ static void record_trace(int argc, char **argv,
if (!ctx->output)
ctx->output = DEFAULT_INPUT_FILE;
+ if (ctx->data_flags & DATA_FL_GUEST)
+ set_vsync_clock();
+
make_instances();
/* Save the state of tracing_on before starting */
--
2.29.2
|