linux-kernel - Re: [PATCH 11/12] perf tools: Reuse shared eBPF dso objects

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Message-ID: <20190417073241.GC17024@krava>
Date:   Wed, 17 Apr 2019 09:32:41 +0200
From:   Jiri Olsa <jolsa@...hat.com>
To:     Adrian Hunter <adrian.hunter@...el.com>
Cc:     Jiri Olsa <jolsa@...nel.org>,
        Arnaldo Carvalho de Melo <acme@...nel.org>,
        lkml <linux-kernel@...r.kernel.org>,
        Ingo Molnar <mingo@...nel.org>,
        Namhyung Kim <namhyung@...nel.org>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Peter Zijlstra <a.p.zijlstra@...llo.nl>,
        Andi Kleen <ak@...ux.intel.com>,
        Song Liu <songliubraving@...com>,
        Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>
Subject: Re: [PATCH 11/12] perf tools: Reuse shared eBPF dso objects

On Wed, Apr 17, 2019 at 09:55:25AM +0300, Adrian Hunter wrote:
> On 17/04/19 9:51 AM, Jiri Olsa wrote:
> > On Wed, Apr 17, 2019 at 09:35:32AM +0300, Adrian Hunter wrote:
> >> On 16/04/19 7:01 PM, Jiri Olsa wrote:
> >>> The eBPF program can be loaded multiple times
> >>> with the same name (tag). We can share dso
> >>> objects for those programs.
> >>
> >> Doesn't a eBPF program get recompiled differently every time it is loaded?
> > 
> > yes, but those with same tag are identical
> 
> But won't recompiled eBPF programs be different due to blinded constants?
> Or perhaps in the future other code randomization?

ah right.. that can happen, let's skip this one then

perhaps we could add bpf prog id to be part of the name
to make it unique.. I'll check

thanks,
jirka

> 
> > 
> > jirka
> > 
> >>
> >>>
> >>> Link: http://lkml.kernel.org/n/tip-3damf8vq1dryhtpbk5b06jpt@git.kernel.org
> >>> Signed-off-by: Jiri Olsa <jolsa@...nel.org>
> >>> ---
> >>>  tools/perf/util/machine.c | 14 +++++++++++---
> >>>  1 file changed, 11 insertions(+), 3 deletions(-)
> >>>
> >>> diff --git a/tools/perf/util/machine.c b/tools/perf/util/machine.c
> >>> index d4aa44489011..a60653827891 100644
> >>> --- a/tools/perf/util/machine.c
> >>> +++ b/tools/perf/util/machine.c
> >>> @@ -23,6 +23,7 @@
> >>>  #include "linux/hash.h"
> >>>  #include "asm/bug.h"
> >>>  #include "bpf-event.h"
> >>> +#include "dso.h"
> >>>  
> >>>  #include "sane_ctype.h"
> >>>  #include <symbol/kallsyms.h>
> >>> @@ -699,11 +700,18 @@ static int machine__process_ksymbol_register(struct machine *machine,
> >>>  
> >>>  	map = map_groups__find(&machine->kmaps, event->ksymbol_event.addr);
> >>>  	if (!map) {
> >>> -		map = dso__new_map(event->ksymbol_event.name);
> >>> -		if (!map)
> >>> +		struct dso *dso;
> >>> +
> >>> +		dso = dsos__findnew(&machine->dsos, event->ksymbol_event.name);
> >>> +		if (!dso)
> >>>  			return -ENOMEM;
> >>>  
> >>> -		map->start = event->ksymbol_event.addr;
> >>> +		map = map__new2(event->ksymbol_event.addr, dso);
> >>> +		if (!map) {
> >>> +			dso__put(dso);
> >>> +			return -ENOMEM;
> >>> +		}
> >>> +
> >>>  		map->end = map->start + event->ksymbol_event.len;
> >>>  		map_groups__insert(&machine->kmaps, map);
> >>>  	}
> >>>
> >>
> > 
>