Re: [PATCH v2 2/9] cxl: add helper to parse through all current events

[Alison Schofield <alison.schofield@intel.com>]

On Mon, Sep 19, 2022 at 04:46:46PM -0700, Dave Jiang wrote:
> Add common function to iterate through and extract the events in the
> current trace buffer. The function uses tracefs_iterate_raw_events() from
> libtracefs to go through all the events loaded into a tep_handle. A
> callback is provided to the API call in order to parse the event. For cxl
> monitor, an array of interested "systems" is provided in order to filter
> for the interested events.
> 
> Signed-off-by: Dave Jiang <dave.jiang@intel.com>
> ---
>  cxl/event_trace.c |   33 +++++++++++++++++++++++++++++++++
>  cxl/event_trace.h |    7 +++++++
>  cxl/meson.build   |    1 +
>  meson.build       |    2 ++
>  4 files changed, 43 insertions(+)
> 
> diff --git a/cxl/event_trace.c b/cxl/event_trace.c
> index ffa2a9b9b036..430146ce66f5 100644
> --- a/cxl/event_trace.c
> +++ b/cxl/event_trace.c
> @@ -16,6 +16,7 @@
>  #include <libcxl.h>
>  #include <uuid/uuid.h>
>  #include <traceevent/event-parse.h>
> +#include <tracefs/tracefs.h>
>  #include "json.h"
>  #include "event_trace.h"
>  
> @@ -164,3 +165,35 @@ err_jevent:
>  	free(jnode);
>  	return rc;
>  }
> +
> +static int cxl_event_parse_cb(struct tep_event *event, struct tep_record *record,
> +		int cpu, void *ctx)
> +{
> +	struct event_ctx *event_ctx = (struct event_ctx *)ctx;
> +	int rc;
> +
> +	/* Filter out all the events that the caller isn't interested in. */
> +	if (strcmp(event->system, event_ctx->system) != 0)
> +		return 0;
> +

While integrating w poison events, I find I'd like to filter on 
tep_event->name == "cxl_poison" here.

Something like this:

+	if (event_ctx->name) {
+		if (strcmp(event->name, event_ctx->name) != 0)
+			return 0;
+	}
 
along w this:

struct event_ctx {
 	const char *system;
+	const char *name;
 	struct list_head jlist_head;
 };

I guess an all|1 option won't suffice for users wanting a subset.
See how that fits it w your needs for monitor command. I can always
filter after the fact if this type of change is not generally useful.

Thanks,
Alison


> +	rc = cxl_event_to_json_callback(event, record, &event_ctx->jlist_head);
> +	if (rc < 0)
> +		return rc;
> +
> +	return 0;
> +}
> +
> +int cxl_parse_events(struct tracefs_instance *inst, struct event_ctx *ectx)
> +{
> +	struct tep_handle *tep;
> +	int rc;
> +
> +	tep = tracefs_local_events(NULL);
> +	if (!tep)
> +		return -ENOMEM;
> +
> +	rc = tracefs_iterate_raw_events(tep, inst, NULL, 0,
> +			cxl_event_parse_cb, ectx);
> +	tep_free(tep);
> +	return rc;
> +}
> diff --git a/cxl/event_trace.h b/cxl/event_trace.h
> index 00975a0b5680..2fbefa1586d9 100644
> --- a/cxl/event_trace.h
> +++ b/cxl/event_trace.h
> @@ -11,4 +11,11 @@ struct jlist_node {
>  	struct list_node list;
>  };
>  
> +struct event_ctx {
> +	const char *system;
> +	struct list_head jlist_head;
> +};
> +
> +int cxl_parse_events(struct tracefs_instance *inst, struct event_ctx *ectx);
> +
>  #endif
> diff --git a/cxl/meson.build b/cxl/meson.build
> index 8c7733431613..c59876262e76 100644
> --- a/cxl/meson.build
> +++ b/cxl/meson.build
> @@ -21,6 +21,7 @@ cxl_tool = executable('cxl',
>      json,
>      versiondep,
>      traceevent,
> +    tracefs,
>    ],
>    install : true,
>    install_dir : rootbindir,
> diff --git a/meson.build b/meson.build
> index f611e0bdd7f3..c204c8ac52de 100644
> --- a/meson.build
> +++ b/meson.build
> @@ -143,6 +143,8 @@ libudev = dependency('libudev')
>  uuid = dependency('uuid')
>  json = dependency('json-c')
>  traceevent = dependency('libtraceevent')
> +tracefs = dependency('libtracefs')
> +
>  if get_option('docs').enabled()
>    if get_option('asciidoctor').enabled()
>      asciidoc = find_program('asciidoctor', required : true)
> 
>