[lttng-dev] [PATCH lttng-tools v2 1/3] Enable perf PMU counters by raw ID
Jérémie Galarneau
jeremie.galarneau at efficios.com
Tue Jul 5 02:31:34 UTC 2016
On Wed, Jun 22, 2016 at 3:27 PM, Julien Desfossez
<jdesfossez at efficios.com> wrote:
> 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 allows the user to give a more friendly name.
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 | 94 +++++++++++++++++++++++++++++++++++-
> 2 files changed, 101 insertions(+), 1 deletion(-)
>
> diff --git a/doc/man/lttng-add-context.1.txt b/doc/man/lttng-add-context.1.txt
> index f995a7f..c43581a 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
> +give a symbolic name to the counter in the trace.
...to associate a...
> +
> 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..711c1e0 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 +689,88 @@ end:
> }
>
> static
> +int find_ctx_type_perf_raw(const char *ctx, struct ctx_type *type)
> +{
> + char *next;
Reduce scope of "next" to the "for" loop.
> + int ret;
> + int field_pos = 0;
> + char *tmp_list;
> +
> + tmp_list = strdup(ctx);
> + if (!tmp_list) {
> + PERROR("strdup temp list");
> + ret = -ENOMEM;
> + goto error;
No need for a separate error label to skip the free() as tmp_list is NULL.
> + }
> +
> + /* Looking for "perf:[cpu|thread]:raw:<mask>:<name>". */
> + for (;;) {
> + next = strtok(tmp_list, ":");
> + if (!next) {
> + break;
> + }
> + tmp_list = NULL;
tmp_list is leaked.
> + 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:
> + if (strlen(next) < 2 || next[0] != 'r') {
> + ERR("Wrong perf raw mask format: rNNN");
> + ret = -1;
> + goto end;
> + }
> + type->opt->u.perf.config = strtoll(next + 1, NULL, 16);
strtoll() should be checked for error (setting errno to 0 beforehand,
and checking after for EINVAL and ERANGE, but also using the endptr).
This currently allows, for instance:
lttng add-context -u -t perf:thread:raw:rXYZ:oops
Such malformed cases should be added to the test suite.
> + 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("Wrong perf raw format");
"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);
> +error:
> + 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 +793,18 @@ 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
>
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> lttng-dev at lists.lttng.org
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--
Jérémie Galarneau
EfficiOS Inc.
http://www.efficios.com
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