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SubjectRe: [PATCH 03/24] perf: Add build id data in mmap2 event
On Tue, Nov 10, 2020 at 03:55:06PM -0300, Arnaldo Carvalho de Melo wrote:
> Em Tue, Nov 10, 2020 at 07:23:34PM +0100, Jiri Olsa escreveu:
> > On Tue, Nov 10, 2020 at 11:10:46AM +0100, Jiri Olsa wrote:
> > > On Tue, Nov 10, 2020 at 09:28:51AM +0100, Peter Zijlstra wrote:
> > > > 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.
>
> Agreed.
>
> > > ok
>
> > > >
> > > > 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 ?
> > >
> > > ook
> >
> > how about the change below.. I also switch the build_id with the size,
> > but I kept the build_id size 20, because I think there's bigger chance
> > we will use those reserved bytes for something, than that we will need
> > those extra 3 bytes in build_id array
> >
> > struct {
> > u8 build_id_size;
> > u8 __reserved_1;
> > u16 __reserved_2;
> > u8 build_id[20];
> > };
>
> For "maybe we'll use it for something else" doesn't require that it gets
> before build_id, i.e. to use it for something else it can be as above or
>
> struct {
> u8 build_id_size;
> u8 build_id[20];
> u8 __reserved_1;
> u16 __reserved_2;
> };
>
> that groups build_id size with it, but nah, this is getting funny by
> now.

yep, that's why I kept it like above

>
> My suggestion was not about increasing build_id to 23, just to leave the
> unused (reserved) bytes after it.

ok, thanks

jirka

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