Re: [PATCH v3 2/3] perf: Userspace event

[Namhyung Kim <namhyung@kernel.org>]

Hi Pawel,

On Tue,  4 Nov 2014 00:28:37 +0000, Pawel Moll wrote:
> +	/*
> +	 * Data in userspace event record is transparent for the kernel
> +	 *
> +	 * Userspace perf tool code maintains a list of known types with
> +	 * reference implementations of parsers for the data field.
> +	 *
> +	 * Overall size of the record (including type and size fields)
> +	 * is always aligned to 8 bytes by adding padding after the data.
> +	 *
> +	 * struct {
> +	 *	struct perf_event_header	header;
> +	 *	u32				type;
> +	 *	u32				size;

The struct perf_event_header also has 'size' field and it has the entire
length of the record so it's redundant.  Also there's 'misc' field in the
perf_event_header and I guess it can be used as 'type' info as it's
mostly for cpumode and we are in user mode by definition.

Thanks,
Namhyung


> +	 *	char				data[size];
> +	 *	char				__padding[-size & 7];
> +	 * 	struct sample_id		sample_id;
> +	 * };
> +	 */
> +	PERF_RECORD_UEVENT			= 11,
> +
>  	PERF_RECORD_MAX,			/* non-ABI */
>  };