Re: [PATCH v3 2/5] kernel-shark-2.alpha: Use new tracecmd APIs to open guest tracing file

["Yordan Karadzhov (VMware)" <y.karadz@gmail.com>]

On 16.04.20 г. 19:00 ч., Tzvetomir Stoyanov (VMware) wrote:
> From: Tzvetomir (VMware)  Stoyanov <tz.stoyanov@gmail.com>
> 
> The new tracecmd API tracecmd_open_head() allows opening a trace.dat
> file on stages. First, only the headers from the file are read and parsed,
> without reading the tracing data.
> The tracecmd_pair_peer() API is used to bind a tracing peer to
> this file, before parsing the trace data. This affects events timestamps
> correction when the tracing data is loaded.
> The tracecmd_get_guest_cpumap() API is used to find dependencies between
> all files and find a possible tracing peers.
> 
> This change depends on these trace-cmd patch sets:
>    "Useful APIs for merging tracing files"
> https://patchwork.kernel.org/project/linux-trace-devel/list/?series=268745
>    "Split reading the trace.dat options from trace data"
> https://patchwork.kernel.org/project/linux-trace-devel/list/?series=268743
> 
> Signed-off-by: Tzvetomir (VMware)  Stoyanov <tz.stoyanov@gmail.com>
> ---
>   src/libkshark-tepdata.c | 59 ++++++++++++++++++++++++++++++++++++++++-
>   1 file changed, 58 insertions(+), 1 deletion(-)
> 
> diff --git a/src/libkshark-tepdata.c b/src/libkshark-tepdata.c
> index 8678e12..f280e57 100644
> --- a/src/libkshark-tepdata.c
> +++ b/src/libkshark-tepdata.c
> @@ -985,6 +985,45 @@ const char *tep_plugin_names[] = {"sched_events",
>   
>   #define LINUX_IDLE_TASK_PID	0
>   
> +/** Find a host stream from the same tracing session, that has guest information */
> +struct tracecmd_input *kshark_tep_find_merge_peer(struct kshark_context *kshark_ctx,
> +						  struct tracecmd_input *handle)

This function can be defined static.

> +{
> +	struct tracecmd_input *peer_handle = NULL;
> +	struct kshark_data_stream *peer_stream;
> +	unsigned long long trace_id;
> +	int *streamIds = NULL;

Nit: please stick to "snake_case" in the C code and "camelCase in the 
C++ code.

No need to send new version. I am applying patchs 1-3 from this patch-set.

Thanks a lot!
Yordan

> +	int ret;
> +	int i;
> +
> +	trace_id = tracecmd_get_traceid(handle);
> +	if (!trace_id)
> +		goto out;
> +
> +	streamIds = kshark_all_streams(kshark_ctx);
> +	if (!streamIds)
> +		goto out;
> +	for (i = 0; i < kshark_ctx->n_streams; i++) {
> +		peer_stream = kshark_get_data_stream(kshark_ctx, streamIds[i]);
> +		if (!peer_stream || peer_stream->format != KS_TEP_DATA)
> +			continue;
> +		peer_handle = kshark_get_tep_input(peer_stream);
> +		if (!peer_handle)
> +			continue;
> +		ret = tracecmd_get_guest_cpumap(peer_handle, trace_id,
> +						NULL, NULL, NULL);
> +		if (!ret)
> +			break;
> +	}
> +
> +	if (i == kshark_ctx->n_streams)
> +		peer_handle = NULL;
> +
> +out:
> +	free(streamIds);
> +	return peer_handle;
> +}
> +
>   /** Initialize the FTRACE data input (from file). */
>   int kshark_tep_init_input(struct kshark_data_stream *stream,
>   			  const char *file)
> @@ -992,8 +1031,10 @@ int kshark_tep_init_input(struct kshark_data_stream *stream,
>   	struct kshark_context *kshark_ctx = NULL;
>   	struct tepdata_handle *tep_handle;
>   	struct kshark_plugin_list *plugin;
> +	struct tracecmd_input *merge_peer;
>   	struct tep_event *event;
>   	int i, n_tep_plugins;
> +	int ret;
>   
>   	if (!kshark_instance(&kshark_ctx) || !init_thread_seq())
>   		return -EEXIST;
> @@ -1009,13 +1050,29 @@ int kshark_tep_init_input(struct kshark_data_stream *stream,
>   	if (!tep_handle)
>   		return -EFAULT;
>   
> -	tep_handle->input = tracecmd_open(file);
> +	/** Open the tracing file, parse headers and create trace input context */
> +	tep_handle->input = tracecmd_open_head(file);
>   	if (!tep_handle->input) {
>   		free(tep_handle);
>   		stream->interface.handle = NULL;
>   		return -EEXIST;
>   	}
>   
> +	/** Find a merge peer from the same tracing session */
> +	merge_peer = kshark_tep_find_merge_peer(kshark_ctx, tep_handle->input);
> +	if (merge_peer)
> +		tracecmd_pair_peer(tep_handle->input, merge_peer);
> +
> +	/** Read the racing data from the file */
> +	ret = tracecmd_init_data(tep_handle->input);
> +
> +	if (ret < 0) {
> +		tracecmd_close(tep_handle->input);
> +		free(tep_handle);
> +		stream->interface.handle = NULL;
> +		return -EEXIST;
> +	}
> +
>   	tep_handle->tep = tracecmd_get_pevent(tep_handle->input);
>   
>   	tep_handle->sched_switch_event_id = -EINVAL;
>