[lttng-dev] [PATCH lttng-tools v3 1/3] Enable perf PMU counters by raw ID

[Julien Desfossez]

Allow enabling perf PMU counters by raw ID in addition to the generic
list already provided. The format for kernel tracing is
"perf:cpu:raw:rNNN:<name>" and "perf:thread:raw:rNNN:<name> for
user-space. The rNNN format is the same as perf-record(1) where NNN is a
hexadecimal event descriptor in the form of umask+eventsel. The <name>
field to associate a clearer name to the counter.

Example usage on Intel i7-3520M to get the unhalted reference cycles
(eventsel: 0x13c) count at privilege level 0 (umask: 0x00):
lttng add-context -k -t perf:cpu:raw:r0013c:x86unhalted

Result in the trace:
sched_switch: { cpu_id = 3 }, {
	perf_cpu_raw_r0013c_x86unhalted = 27632578 }, [...]

Signed-off-by: Julien Desfossez <jdesfossez at efficios.com>
---
 doc/man/lttng-add-context.1.txt      |   8 +++
 src/bin/lttng/commands/add_context.c | 106 ++++++++++++++++++++++++++++++++++-
 2 files changed, 113 insertions(+), 1 deletion(-)

diff --git a/doc/man/lttng-add-context.1.txt b/doc/man/lttng-add-context.1.txt
index f995a7f..831646b 100644
--- a/doc/man/lttng-add-context.1.txt
+++ b/doc/man/lttng-add-context.1.txt
@@ -45,6 +45,14 @@ per-thread (`perf:thread:` prefix) counters. Currently, per-CPU counters
 can only be used in the Linux kernel tracing domain, while per-thread
 counters can only be used in the user space tracing domain.
 
+It is also possible to enable PMU counters by raw ID using the
+`perf:cpu:raw:r<N>:<name>` or `perf:thread:raw:r<N>:<name>` format for the
+kernel and user-space respectively. `<N>` is a hexadecimal event descriptor
+which is the same format as perf-record(1): a concatenation of the `Umask
+value` and `Event number` provided by the processors manufacturer. The possible
+values for this field are processor-specific. The `<name>` field is used to
+associate a clearer name to the counter.
+
 Application-specific context fields can be added to a channel using the
 following syntax:
 
diff --git a/src/bin/lttng/commands/add_context.c b/src/bin/lttng/commands/add_context.c
index 2f43dc7..e2fe281 100644
--- a/src/bin/lttng/commands/add_context.c
+++ b/src/bin/lttng/commands/add_context.c
@@ -87,6 +87,7 @@ enum perf_type {
 	PERF_TYPE_HARDWARE = 0,
 	PERF_TYPE_SOFTWARE = 1,
 	PERF_TYPE_HW_CACHE = 3,
+	PERF_TYPE_RAW = 4,
 };
 
 enum perf_count_hard {
@@ -688,9 +689,100 @@ end:
 }
 
 static
+int find_ctx_type_perf_raw(const char *ctx, struct ctx_type *type)
+{
+	int ret;
+	int field_pos = 0;
+	char *tmp_list, *cur_list;
+
+	cur_list = tmp_list = strdup(ctx);
+	if (!tmp_list) {
+		PERROR("strdup temp list");
+		ret = -ENOMEM;
+		goto end;
+	}
+
+	/* Looking for "perf:[cpu|thread]:raw:<mask>:<name>". */
+	for (;;) {
+		char *next;
+
+		next = strtok(cur_list, ":");
+		if (!next) {
+			break;
+		}
+		cur_list = NULL;
+		switch (field_pos) {
+		case 0:
+			if (strncmp(next, "perf", 4) != 0) {
+				ret = -1;
+				goto end;
+			}
+			break;
+		case 1:
+			if (strncmp(next, "cpu", 3) == 0) {
+				type->opt->ctx_type = CONTEXT_PERF_CPU_COUNTER;
+			} else if (strncmp(next, "thread", 4) == 0) {
+				type->opt->ctx_type = CONTEXT_PERF_THREAD_COUNTER;
+			} else {
+				ret = -1;
+				goto end;
+			}
+			break;
+		case 2:
+			if (strncmp(next, "raw", 3) != 0) {
+				ret = -1;
+				goto end;
+			}
+			break;
+		case 3:
+		{
+			char *endptr;
+
+			if (strlen(next) < 2 || next[0] != 'r') {
+				ERR("Wrong perf raw mask format: rNNN");
+				ret = -1;
+				goto end;
+			}
+			errno = 0;
+			type->opt->u.perf.config = strtoll(next +  1, &endptr, 16);
+			if (errno != 0 || !endptr || *endptr) {
+				ERR("Wrong perf raw mask format: rNNN");
+				ret = -1;
+				goto end;
+			}
+			break;
+		}
+		case 4:
+			/* name */
+			break;
+		case 5:
+			ERR("Too many ':' in perf raw format");
+			ret = -1;
+			goto end;
+		};
+		field_pos++;
+	}
+
+	if (field_pos < 5) {
+		ERR("Invalid perf counter specifier, expected a specifier of "
+			"the form perf:cpu:raw:rNNN:<name> or "
+			"perf:thread:raw:rNNN:<name>");
+		ret = -1;
+		goto end;
+	}
+
+	ret = 0;
+	goto end;
+
+end:
+	free(tmp_list);
+	return ret;
+}
+
+static
 struct ctx_type *get_context_type(const char *ctx)
 {
-	int opt_index;
+	int opt_index, ret;
 	struct ctx_type *type = NULL;
 	const char app_ctx_prefix[] = "$app.";
 	char *provider_name = NULL, *ctx_name = NULL;
@@ -713,6 +805,18 @@ struct ctx_type *get_context_type(const char *ctx)
 		goto found;
 	}
 
+	/* Check if ctx is a raw perf context. */
+	ret = find_ctx_type_perf_raw(ctx, type);
+	if (ret == 0) {
+		type->opt->u.perf.type = PERF_TYPE_RAW;
+		type->opt->symbol = strdup(ctx);
+		if (!type->opt->symbol) {
+			PERROR("Copy perf field name");
+			goto not_found;
+		}
+		goto found;
+	}
+
 	/*
 	 * No match found against static contexts; check if it is an app
 	 * context.
-- 
1.9.1