perf record: Implement COMPRESSED event record and its attributes

Implemented PERF_RECORD_COMPRESSED event, related data types, header
feature and functions to write, read and print feature attributes from
the trace header section.

comp_mmap_len preserves the size of mmaped kernel buffer that was used
during collection. comp_mmap_len size is used on loading stage as the
size of decomp buffer for decompression of COMPRESSED events content.

Committer notes:

Fixed up conflict with BPF_PROG_INFO and BTF_BTF header features.

Signed-off-by: Alexey Budankov <alexey.budankov@linux.intel.com>
Reviewed-by: Jiri Olsa <jolsa@kernel.org>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Andi Kleen <ak@linux.intel.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/r/ebbaf031-8dda-3864-ebc6-7922d43ee515@linux.intel.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

tools/perf/Documentation/perf.data-file-format.txt

@@ -272,6 +272,19 @@ struct {
 
 Two uint64_t for the time of first sample and the time of last sample.
 
+        HEADER_COMPRESSED = 27,
+
+struct {
+	u32	version;
+	u32	type;
+	u32	level;
+	u32	ratio;
+	u32	mmap_len;
+};
+
+Indicates that trace contains records of PERF_RECORD_COMPRESSED type
+that have perf_events records in compressed form.
+
 	other bits are reserved and should ignored for now
 	HEADER_FEAT_BITS	= 256,
 
@@ -437,6 +450,17 @@ struct auxtrace_error_event {
 Describes a header feature. These are records used in pipe-mode that
 contain information that otherwise would be in perf.data file's header.
 
+	PERF_RECORD_COMPRESSED 			= 81,
+
+struct compressed_event {
+	struct perf_event_header	header;
+	char				data[];
+};
+
+The header is followed by compressed data frame that can be decompressed
+into array of perf trace records. The size of the entire compressed event
+record including the header is limited by the max value of header.size.
+
 Event types
 
 Define the event attributes with their IDs.