linux-kernel - Re: [PATCH 6/9] perf tools: Don't search for active kernel start in __machine__create_kernel

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Message-ID: <20180219100140.GA17630@krava>
Date:   Mon, 19 Feb 2018 11:01:40 +0100
From:   Jiri Olsa <jolsa@...hat.com>
To:     Namhyung Kim <namhyung@...nel.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>,
        David Ahern <dsahern@...il.com>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Peter Zijlstra <a.p.zijlstra@...llo.nl>, kernel-team@....com
Subject: Re: [PATCH 6/9] perf tools: Don't search for active kernel start in
 __machine__create_kernel_maps

On Mon, Feb 19, 2018 at 11:20:36AM +0900, Namhyung Kim wrote:

SNIP

> > +static void machine__set_kernel_mmap(struct machine *machine,
> > +				     u64 start, u64 end)
> > +{
> > +	int i;
> > +
> > +	for (i = 0; i < MAP__NR_TYPES; i++) {
> > +		machine->vmlinux_maps[i]->start = start;
> > +		machine->vmlinux_maps[i]->end   = end;
> > +
> > +		/*
> > +		 * Be a bit paranoid here, some perf.data file came with
> > +		 * a zero sized synthesized MMAP event for the kernel.
> > +		 */
> > +		if (machine->vmlinux_maps[i]->end == 0)
> > +			machine->vmlinux_maps[i]->end = ~0ULL;
> 
> Hmm.. this will make map_groups__fixup_end() below not working since
> it only updates if the end address of a map is zero.
> 
> And about the paranoid check, AFAIK the only case it cares is the
> machine__process_kernel_mmap_event() which calls it with
> event->mmap.start and event->mmap.start + event->mmap.len.  Thus, in
> order for the end to be zero, both start and len should be zero.  Then
> I think this condition can be changed like below:
> 
> diff --git a/tools/perf/util/machine.c b/tools/perf/util/machine.c
> index fe27ef55cbb9..c8acb603c359 100644
> --- a/tools/perf/util/machine.c
> +++ b/tools/perf/util/machine.c
> @@ -1226,7 +1226,7 @@ static void machine__set_kernel_mmap(struct machine *machine,
>                  * Be a bit paranoid here, some perf.data file came with
>                  * a zero sized synthesized MMAP event for the kernel.
>                  */
> -               if (machine->vmlinux_maps[i]->end == 0)
> +               if (start == 0 && end == 0)
>                         machine->vmlinux_maps[i]->end = ~0ULL;
>         }

right, the call from machine__create_kernel_maps will have always
the start != 0 and there will be subsequent map_groups__fixup_end
call..

seems ok to me.. will you send the patch?

thanks,
jirka