Re: [PATCH 03/24] perf: Add build id data in mmap2 event

[Peter Zijlstra]

On Mon, Nov 09, 2020 at 10:53:54PM +0100, Jiri Olsa wrote:
> There's new misc bit for mmap2 to signal there's build
> id data in it:
> 
>   #define PERF_RECORD_MISC_BUILD_ID              (1 << 14)

PERF_RECORD_MISC_MMAP_BUILD_ID would be consistent with the existing
PERF_RECORD_MISC_MMAP_DATA naming.

Also, AFAICT there's still a bunch of unused bits in misc.

	012	    CDEF
	|||---------||||

Where:
	0-2	CPUMODE_MASK

	C	PROC_MAP_PARSE_TIMEOUT
	D	MMAP_DATA / COMM_EXEC / FORK_EXEC / SWITCH_OUT
	E	EXACT_IP / SCHED_OUT_PREEMPT
	F	(reserved)

Maybe we should put in a comment to keep track of the hole ?

Also, perhaps it is time to use F to indicate that @size is in 8 instead
of 1 ? That would increase our max entry size to 512K, people seem to
hit his 64K limit (insane as it is).