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From: Steven Rostedt <rostedt@goodmis.org>
To: "Tzvetomir Stoyanov (VMware)" <tz.stoyanov@gmail.com>
Cc: linux-trace-devel@vger.kernel.org
Subject: Re: [PATCH v17 06/18] trace-cmd: Add new library API for reading ftrace buffers
Date: Wed, 4 Dec 2019 16:10:50 -0500
Message-ID: <20191204161050.16ab1910@gandalf.local.home> (raw)
In-Reply-To: <20191203103522.482684-7-tz.stoyanov@gmail.com>

On Tue,  3 Dec 2019 12:35:10 +0200
"Tzvetomir Stoyanov (VMware)" <tz.stoyanov@gmail.com> wrote:

> A new libtracecmd API is introduced:
> 
> 	int tracecmd_iterate_raw_events(struct tep_handle *tep,
> 					struct tracecmd_instance *instance,
> 					int (*callback)(struct tep_event *,
> 						   	struct tep_record *,
> 						   	int, void *context),
> 					void *callback_context);
> 
> It reads events from trace_pipe_raw, per cpu ftrace buffer, and calls a user
> callback for each of them. The API is instance aware.

Hmm, would be good to know what this would be used for.

> 
> Signed-off-by: Tzvetomir Stoyanov (VMware) <tz.stoyanov@gmail.com>
> ---
>  include/trace-cmd/trace-cmd.h |   8 +++
>  lib/trace-cmd/trace-util.c    | 114 ++++++++++++++++++++++++++++++++++
>  2 files changed, 122 insertions(+)
> 
> diff --git a/include/trace-cmd/trace-cmd.h b/include/trace-cmd/trace-cmd.h
> index 5d4292e..831bb1a 100644
> --- a/include/trace-cmd/trace-cmd.h
> +++ b/include/trace-cmd/trace-cmd.h
> @@ -380,6 +380,14 @@ char *tracecmd_read_instance_file(struct tracecmd_instance *instance,
>  
>  void tracecmd_set_clock(struct tracecmd_instance *instance, char **old_clock);
>  
> +int tracecmd_iterate_raw_events(struct tep_handle *tep,
> +				struct tracecmd_instance *instance,
> +				   int (*callback)(struct tep_event *,
> +						   struct tep_record *,
> +						   int, void *context),
> +				void *callback_context);
> +
> +
>  
>  /* --- Plugin handling --- */
>  extern struct tep_plugin_option trace_ftrace_options[];
> diff --git a/lib/trace-cmd/trace-util.c b/lib/trace-cmd/trace-util.c
> index e019dce..a54a905 100644
> --- a/lib/trace-cmd/trace-util.c
> +++ b/lib/trace-cmd/trace-util.c
> @@ -1185,3 +1185,117 @@ int tracecmd_write_file(const char *file, const char *str, const char *type)
>  	}
>  	return ret;
>  }
> +
> +static int
> +get_events_in_page(struct tep_handle *tep, void *page,
> +		   int size, int cpu,
> +		   int (*callback)(struct tep_event *,
> +				   struct tep_record *,
> +				   int, void *),
> +		   void *callback_context)
> +{
> +	struct tep_record *last_record = NULL;
> +	struct tep_event *event = NULL;
> +	struct tep_record *record;
> +	int id, cnt = 0;
> +
> +	if (size <= 0)
> +		return 0;
> +
> +	while (true) {
> +		event = NULL;
> +		record = tracecmd_read_page_record(tep, page, size,
> +						   last_record);
> +		if (!record)
> +			break;
> +		free_record(last_record);
> +		id = tep_data_type(tep, record);
> +		event = tep_find_event(tep, id);
> +		if (event && callback) {
> +			if (callback(event, record, cpu, callback_context))

Hmm, need to be documented that breaking out of the loop will likely
call future reads to lose events. The records on the page after the
record that causes the break will be lost from future reads.

-- Steve



> +				break;
> +		}
> +		last_record = record;
> +	}
> +	free_record(last_record);
> +
> +	return cnt;
> +}
> +
> +/*
> + * tracecmd_iterate_raw_events - Iterate through events in trace_pipe_raw
> + *				 per CPU trace files
> + * @tep: a handle to the trace event parser context
> + * @instance: ftrace instance, can be NULL for the top instance
> + * @callback: A user function, called for each record from the file.
> + * @callback_context: A custom context, passed to the user callback function
> + *
> + * If the @callback returns non-zero, the iteration stops.
> + *
> + * Returns -1 in case of an error, or 0 otherwise.
> + */
> +int tracecmd_iterate_raw_events(struct tep_handle *tep,
> +				struct tracecmd_instance *instance,
> +				int (*callback)(struct tep_event *,
> +						struct tep_record *,
> +						int, void *),
> +				void *callback_context)
> +{
> +	unsigned int p_size;
> +	struct dirent *dent;
> +	char file[PATH_MAX];
> +	void *page = NULL;
> +	struct stat st;
> +	char *path;
> +	DIR *dir;
> +	int ret;
> +	int cpu;
> +	int fd;
> +	int r;
> +
> +	p_size = getpagesize();
> +	path = tracecmd_get_instance_file(instance, "per_cpu");
> +	if (!path)
> +		return -1;
> +	dir = opendir(path);
> +	if (!dir) {
> +		ret = -1;
> +		goto error;
> +	}
> +	page = malloc(p_size);
> +	if (!page) {
> +		ret = -1;
> +		goto error;
> +	}
> +	while ((dent = readdir(dir))) {
> +		const char *name = dent->d_name;
> +
> +		if (strlen(name) < 4 || strncmp(name, "cpu", 3) != 0)
> +			continue;
> +		cpu = atoi(name + 3);
> +		sprintf(file, "%s/%s", path, name);
> +		ret = stat(file, &st);
> +		if (ret < 0 || !S_ISDIR(st.st_mode))
> +			continue;
> +
> +		sprintf(file, "%s/%s/trace_pipe_raw", path, name);
> +		fd = open(file, O_RDONLY | O_NONBLOCK);
> +		if (fd < 0)
> +			continue;
> +		do {
> +			r = read(fd, page, p_size);
> +			if (r > 0)
> +				get_events_in_page(tep, page, r, cpu,
> +						   callback, callback_context);
> +		} while (r > 0);
> +		close(fd);
> +	}
> +	ret = 0;
> +
> +error:
> +	if (dir)
> +		closedir(dir);
> +	free(page);
> +	tracecmd_put_tracing_file(path);
> +	return ret;
> +}


  reply index

Thread overview: 37+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-12-03 10:35 [PATCH v17 00/18]Timestamp synchronization of host - guest tracing session Tzvetomir Stoyanov (VMware)
2019-12-03 10:35 ` [PATCH v17 01/18] trace-cmd: Implement new lib API: tracecmd_local_events_system() Tzvetomir Stoyanov (VMware)
2019-12-03 10:35 ` [PATCH v17 02/18] trace-cmd: Add support for negative time offsets in trace.dat file Tzvetomir Stoyanov (VMware)
2019-12-03 10:35 ` [PATCH v17 03/18] trace-cmd: Add implementations of htonll() and ntohll() Tzvetomir Stoyanov (VMware)
2019-12-03 10:35 ` [PATCH v17 04/18] trace-cmd: Add new library APIs for ftrace instances Tzvetomir Stoyanov (VMware)
2019-12-04 16:17   ` Steven Rostedt
2019-12-05 14:40     ` Tzvetomir Stoyanov
2019-12-03 10:35 ` [PATCH v17 05/18] trace-cmd: Add new library API for local CPU count Tzvetomir Stoyanov (VMware)
2019-12-04 20:09   ` Steven Rostedt
2019-12-03 10:35 ` [PATCH v17 06/18] trace-cmd: Add new library API for reading ftrace buffers Tzvetomir Stoyanov (VMware)
2019-12-04 21:10   ` Steven Rostedt [this message]
2019-12-03 10:35 ` [PATCH v17 07/18] trace-cmd: Find and store pids of tasks, which run virtual CPUs of given VM Tzvetomir Stoyanov (VMware)
2019-12-04 21:35   ` Steven Rostedt
2019-12-03 10:35 ` [PATCH v17 08/18] trace-cmd: Implement new API tracecmd_add_option_v() Tzvetomir Stoyanov (VMware)
2019-12-04 21:47   ` Steven Rostedt
2019-12-03 10:35 ` [PATCH v17 09/18] trace-cmd: Add new API to generate a unique ID of the tracing session Tzvetomir Stoyanov (VMware)
2019-12-03 10:35 ` [PATCH v17 10/18] trace-cmd: Store the session tracing ID in the trace.dat file Tzvetomir Stoyanov (VMware)
2019-12-03 10:35 ` [PATCH v17 11/18] trace-cmd: Exchange tracing IDs between host and guest Tzvetomir Stoyanov (VMware)
2019-12-04 22:03   ` Steven Rostedt
2019-12-03 10:35 ` [PATCH v17 12/18] trace-cmd: Implement new option in trace.dat file: TRACECMD_OPTION_TIME_SHIFT Tzvetomir Stoyanov (VMware)
2019-12-05  0:46   ` Steven Rostedt
2019-12-05 15:09     ` Tzvetomir Stoyanov
2019-12-03 10:35 ` [PATCH v17 13/18] trace-cmd: Add guest information in host's trace.dat file Tzvetomir Stoyanov (VMware)
2019-12-05  0:59   ` Steven Rostedt
2019-12-03 10:35 ` [PATCH v17 14/18] trace-cmd: Add host trace clock as guest trace argument Tzvetomir Stoyanov (VMware)
2019-12-09 19:31   ` Steven Rostedt
2019-12-10  8:49     ` Tzvetomir Stoyanov
2019-12-10 15:48       ` Steven Rostedt
2019-12-11  8:21         ` Tzvetomir Stoyanov
2019-12-11 15:01           ` Steven Rostedt
2019-12-03 10:35 ` [PATCH v17 15/18] trace-cmd: Refactor few trace-cmd internal functions Tzvetomir Stoyanov (VMware)
2019-12-09 19:32   ` Steven Rostedt
2019-12-03 10:35 ` [PATCH v17 16/18] trace-cmd: Basic infrastructure for host - guest timestamp synchronization Tzvetomir Stoyanov (VMware)
2019-12-10 17:04   ` Steven Rostedt
2019-12-10 18:39   ` Steven Rostedt
2019-12-03 10:35 ` [PATCH v17 17/18] trace-cmd: [POC] PTP-like algorithm " Tzvetomir Stoyanov (VMware)
2019-12-03 10:35 ` [PATCH v17 18/18] trace-cmd: Debug scripts for " Tzvetomir Stoyanov (VMware)

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