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

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Message-ID: <20201110101041.GC387652@krava>
Date:   Tue, 10 Nov 2020 11:10:41 +0100
From:   Jiri Olsa <jolsa@...hat.com>
To:     Peter Zijlstra <peterz@...radead.org>
Cc:     Jiri Olsa <jolsa@...nel.org>,
        Arnaldo Carvalho de Melo <acme@...nel.org>,
        lkml <linux-kernel@...r.kernel.org>,
        Ingo Molnar <mingo@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Namhyung Kim <namhyung@...nel.org>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Michael Petlan <mpetlan@...hat.com>,
        Song Liu <songliubraving@...com>,
        Ian Rogers <irogers@...gle.com>,
        Stephane Eranian <eranian@...gle.com>,
        Alexey Budankov <alexey.budankov@...ux.intel.com>,
        Andi Kleen <ak@...ux.intel.com>,
        Adrian Hunter <adrian.hunter@...el.com>
Subject: Re: [PATCH 03/24] perf: Add build id data in mmap2 event

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.

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

> 
> 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).

nice idea, todo updated ;-)

thanks,
jirka