On 2022-10-25 11:00, David Marchand wrote:
Register telemetry commands to list and configure trace points and later
save traces for a running DPDK application.
Example with testpmd running with two net/null ports (startup command
from devtools/test-null.sh):
--> /trace/list,lib.ethdev.*
{"/trace/list": {"lib.ethdev.configure": false,
"lib.ethdev.rxq.setup": false,
"lib.ethdev.txq.setup": false,
"lib.ethdev.start": false,
"lib.ethdev.stop": false,
"lib.ethdev.close": false,
"lib.ethdev.rx.burst": false,
"lib.ethdev.tx.burst": false}}
--> /trace/enable,lib.ethdev.st*
{"/trace/enable": {"Count": 2}}
--> /trace/enable,lib.ethdev.st*
{"/trace/enable": {"Count": 0}}
--> /trace/list,lib.ethdev.*
{"/trace/list": {"lib.ethdev.configure": false,
"lib.ethdev.rxq.setup": false,
"lib.ethdev.txq.setup": false,
"lib.ethdev.start": true,
"lib.ethdev.stop": true,
"lib.ethdev.close": false,
"lib.ethdev.rx.burst": false,
"lib.ethdev.tx.burst": false}}
testpmd> stop
...
testpmd> port stop all
...
testpmd> port start all
...
testpmd> start
...
--> /trace/save
{"/trace/save": {"Status": "OK",
"Path": ".../dpdk-traces/rte-2022-10-12-AM-10-51-48"}}
$ babeltrace .../dpdk-traces/rte-2022-10-12-AM-10-51-48
[10:51:36.229878723] (+?.?????????) lib.ethdev.stop:
{ cpu_id = 0x0, name = "dpdk-testpmd" }, { port_id = 0x0, ret = 0 }
[10:51:36.229880251] (+0.000001528) lib.ethdev.stop:
{ cpu_id = 0x0, name = "dpdk-testpmd" }, { port_id = 0x1, ret = 0 }
[10:51:40.449359774] (+4.219479523) lib.ethdev.start:
{ cpu_id = 0x0, name = "dpdk-testpmd" }, { port_id = 0x0 }
[10:51:40.449377877] (+0.000018103) lib.ethdev.start:
{ cpu_id = 0x0, name = "dpdk-testpmd" }, { port_id = 0x1 }
--> /trace/disable,*
{"/trace/disable": {"Count": 2}}
Signed-off-by: David Marchand <david.march...@redhat.com>
Acked-by: Jerin Jacob <jer...@marvell.com>
---
Changes since v2:
- separated telemetry change in a dedicated patch,
- switched to boolean types,
Changes since v1:
- added a note in the documentation,
---
doc/guides/prog_guide/trace_lib.rst | 39 +++++++++++++++
lib/eal/common/eal_common_trace.c | 78 +++++++++++++++++++++++++++++
2 files changed, 117 insertions(+)
diff --git a/doc/guides/prog_guide/trace_lib.rst
b/doc/guides/prog_guide/trace_lib.rst
index 9a8f38073d..d0a6bdae4c 100644
--- a/doc/guides/prog_guide/trace_lib.rst
+++ b/doc/guides/prog_guide/trace_lib.rst
@@ -233,6 +233,45 @@ This section steps you through the details of generating
trace and viewing it.
babeltrace $HOME/dpdk-traces/rte-yyyy-mm-dd-[AP]M-hh-mm-ss/
+Configuring traces on a running DPDK application
+------------------------------------------------
+
+The DPDK trace library can be configured using the Telemetry interface.
+
+Examples::
+
+ --> /trace/list,lib.ethdev.*
+ {"/trace/list": {"lib.ethdev.configure": false,
+ "lib.ethdev.rxq.setup": false,
+ "lib.ethdev.txq.setup": false,
+ "lib.ethdev.start": false,
+ "lib.ethdev.stop": false,
+ "lib.ethdev.close": false,
+ "lib.ethdev.rx.burst": false,
+ "lib.ethdev.tx.burst": false}}
+
+ --> /trace/enable,lib.ethdev.st*
+ {"/trace/enable": {"Count": 2}}
+ --> /trace/enable,lib.ethdev.st*
+ {"/trace/enable": {"Count": 0}}
+
+ --> /trace/list,lib.ethdev.*
+ {"/trace/list": {"lib.ethdev.configure": false,
+ "lib.ethdev.rxq.setup": false,
+ "lib.ethdev.txq.setup": false,
+ "lib.ethdev.start": true,
+ "lib.ethdev.stop": true,
+ "lib.ethdev.close": false,
+ "lib.ethdev.rx.burst": false,
+ "lib.ethdev.tx.burst": false}}
+
+ --> /trace/save
+ {"/trace/save": {"Status": "OK",
+ "Path": ".../dpdk-traces/rte-2022-10-12-AM-10-51-48"}}
+
+For more information on how to use the Telemetry interface, see
+the :doc:`../howto/telemetry`.
+
Implementation details
----------------------
diff --git a/lib/eal/common/eal_common_trace.c b/lib/eal/common/eal_common_trace.c
index 5caaac8e59..bb26af618a 100644
--- a/lib/eal/common/eal_common_trace.c
+++ b/lib/eal/common/eal_common_trace.c
@@ -12,6 +12,7 @@
#include <rte_lcore.h>
#include <rte_per_lcore.h>
#include <rte_string_fns.h>
+#include <rte_telemetry.h>
#include "eal_trace.h"
@@ -521,3 +522,80 @@ __rte_trace_point_register(rte_trace_point_t *handle, const char *name,
return -rte_errno;
}
+
+static int
+trace_telemetry_enable(const char *cmd __rte_unused,
+ const char *params, struct rte_tel_data *d)
+{
+ unsigned int count;
status is uint32_t.
+
+ if (params == NULL || strlen(params) == 0)
+ return -1;
+ rte_tel_data_start_dict(d);
+ count = __atomic_load_n(&trace.status, __ATOMIC_RELAXED);
+ rte_trace_pattern(params, true);
+ rte_tel_data_add_dict_int(d, "Count",
+ __atomic_load_n(&trace.status, __ATOMIC_RELAXED) - count);
Why "Count"? From what I could tell, trace.status tells if tracing is
enabled or not.
I also don't understand why &trace.status is loaded twice, especially in
the light that future compilers, that more heavily optimize atomics,
might merge those two loads into one, resulting in something equivalent to:
rte_tel_data_add_dict_int(d, "Count", 0);
Is one of the loads supposed to be a store (or, lock add, rather),
enabling the tracing?
Might be worth to wrap all the atomics in functions, making the code
more clear.
+ return 0;
+
+}
+
+static int
+trace_telemetry_disable(const char *cmd __rte_unused,
+ const char *params, struct rte_tel_data *d)
+{
+ unsigned int count;
+
+ if (params == NULL || strlen(params) == 0)
+ return -1;
+ rte_tel_data_start_dict(d);
+ count = __atomic_load_n(&trace.status, __ATOMIC_RELAXED);
+ rte_trace_pattern(params, false);
+ rte_tel_data_add_dict_int(d, "Count",
+ count - __atomic_load_n(&trace.status, __ATOMIC_RELAXED));
+ return 0;
+
+}
+
+static int
+trace_telemetry_list(const char *cmd __rte_unused,
+ const char *params, struct rte_tel_data *d)
+{
+ struct trace_point *tp;
+
+ rte_tel_data_start_dict(d);
+ STAILQ_FOREACH(tp, &tp_list, next) {
+ if (params != NULL && fnmatch(params, tp->name, 0) != 0)
+ continue;
+
+ rte_tel_data_add_dict_bool(d, tp->name,
+ rte_trace_point_is_enabled(tp->handle));
+ }
+
+ return 0;
+}
+
+static int
+trace_telemetry_save(const char *cmd __rte_unused,
+ const char *params __rte_unused, struct rte_tel_data *d)
+{
+ struct trace *trace = trace_obj_get();
+
+ rte_tel_data_start_dict(d);
+ rte_tel_data_add_dict_string(d, "Status", rte_trace_save() == 0 ? "OK" :
"KO");
+ rte_tel_data_add_dict_string(d, "Path", trace->dir);
+
+ return 0;
+}
+
+RTE_INIT(trace_telemetry)
+{
+ rte_telemetry_register_cmd("/trace/enable", trace_telemetry_enable,
+ "Enable trace points matching the provided pattern. Parameters:
string pattern.");
+ rte_telemetry_register_cmd("/trace/disable", trace_telemetry_disable,
+ "Disable trace points matching the provided pattern. Parameters:
string pattern.");
+ rte_telemetry_register_cmd("/trace/list", trace_telemetry_list,
+ "List trace points. Parameters: string pattern.");
+ rte_telemetry_register_cmd("/trace/save", trace_telemetry_save,
+ "Save current traces. Takes no parameter.");
+}
