Re: [PATCH] perf, report: use properly build_id kernel binaries

[Frederic Weisbecker]

On Fri, Jun 17, 2011 at 02:38:56PM +0200, Jiri Olsa wrote:
> hi, any feedback?
> 
> thanks,
> jirka

I prefer to let that for Arnaldo when he's back. I don't know well
the build-id part.

Thanks.

> 
> On Wed, Jun 01, 2011 at 09:43:46PM +0200, Jiri Olsa wrote:
> > If we bring the recorded perf data together with kernel
> > binary from another machine using:
> > 
> > 	on server A:
> > 	perf archive
> > 
> > 	on server B:
> > 	tar xjvf perf.data.tar.bz2 -C ~/.debug
> > 
> > the build_id kernel dso is not properly recognized during
> > the "perf report" command on server B.
> > 
> > The reason is, that build_id dsos are added during the session initialization,
> > while the kernel maps are created during the sample event processing.
> > 
> > The machine__create_kernel_maps functions ends up creating new dso object
> > for kernel, but it does not check if we already have one added by build_id
> > processing.
> > 
> > 
> > Also the build_id reading ABI quirk added in commit:
> > 
> >  - commit b25114817a73bbd2b84ce9dba02ee1ef8989a947
> >    perf build-id: Add quirk to deal with perf.data file format breakage
> > 
> > populates the "struct build_id_event::pid" with 0, which
> > is later interpreted as DEFAULT_GUEST_KERNEL_ID.
> > 
> > This is not always correct, so it's better to guess the pid
> > value based on the "struct build_id_event::header::misc" value.
> > 
> > 
> > - Tested with data generated on x86 kernel version v2.6.34
> >   and reported back on x86_64 current kernel.
> > - Not tested for guest kernel case.
> > 
> > 
> > Note the problem stays for PERF_RECORD_MMAP events recorded by perf that
> > does not use proper pid (HOST_KERNEL_ID/DEFAULT_GUEST_KERNEL_ID). They are
> > misinterpreted within the current perf code. Probably there's not much we
> > can do about that.
> > 
> > 
> > Signed-off-by: Jiri Olsa <jolsa@xxxxxxxxxx>
> > ---
> >  tools/perf/util/header.c |   11 ++++++++-
> >  tools/perf/util/symbol.c |   57 +++++++++++++++++++++++++--------------------
> >  tools/perf/util/symbol.h |    1 -
> >  3 files changed, 42 insertions(+), 27 deletions(-)
> > 
> > diff --git a/tools/perf/util/header.c b/tools/perf/util/header.c
> > index afb0849..a0d90b1 100644
> > --- a/tools/perf/util/header.c
> > +++ b/tools/perf/util/header.c
> > @@ -726,7 +726,16 @@ static int perf_header__read_build_ids_abi_quirk(struct perf_header *header,
> >  			return -1;
> >  
> >  		bev.header = old_bev.header;
> > -		bev.pid	   = 0;
> > +
> > +		/*
> > +		 * As the pid is the missing value, we need to fill
> > +		 * it properly. The header.misc value give us nice hint.
> > +		 */
> > +		bev.pid	= HOST_KERNEL_ID;
> > +		if (bev.header.misc == PERF_RECORD_MISC_GUEST_USER ||
> > +		    bev.header.misc == PERF_RECORD_MISC_GUEST_KERNEL)
> > +			bev.pid	= DEFAULT_GUEST_KERNEL_ID;
> > +
> >  		memcpy(bev.build_id, old_bev.build_id, sizeof(bev.build_id));
> >  		__event_process_build_id(&bev, filename, session);
> >  
> > diff --git a/tools/perf/util/symbol.c b/tools/perf/util/symbol.c
> > index eec1963..c307121 100644
> > --- a/tools/perf/util/symbol.c
> > +++ b/tools/perf/util/symbol.c
> > @@ -2170,27 +2170,22 @@ size_t machines__fprintf_dsos_buildid(struct rb_root *machines,
> >  	return ret;
> >  }
> >  
> > -struct dso *dso__new_kernel(const char *name)
> > +static struct dso*
> > +dso__kernel_findnew(struct machine *machine, const char *name,
> > +		    const char *short_name, int dso_type)
> >  {
> > -	struct dso *dso = dso__new(name ?: "[kernel.kallsyms]");
> > -
> > -	if (dso != NULL) {
> > -		dso__set_short_name(dso, "[kernel]");
> > -		dso->kernel = DSO_TYPE_KERNEL;
> > -	}
> > -
> > -	return dso;
> > -}
> > +	/*
> > +	 * The kernel dso could be created by build_id processing.
> > +	 */
> > +	struct dso *dso = __dsos__findnew(&machine->kernel_dsos, name);
> >  
> > -static struct dso *dso__new_guest_kernel(struct machine *machine,
> > -					const char *name)
> > -{
> > -	char bf[PATH_MAX];
> > -	struct dso *dso = dso__new(name ?: machine__mmap_name(machine, bf,
> > -							      sizeof(bf)));
> > +	/*
> > +	 * We need to run this in all cases, since during the build_id
> > +	 * processing we had no idea this was the kernel dso.
> > +	 */
> >  	if (dso != NULL) {
> > -		dso__set_short_name(dso, "[guest.kernel]");
> > -		dso->kernel = DSO_TYPE_GUEST_KERNEL;
> > +		dso__set_short_name(dso, short_name);
> > +		dso->kernel = dso_type;
> >  	}
> >  
> >  	return dso;
> > @@ -2208,24 +2203,36 @@ void dso__read_running_kernel_build_id(struct dso *dso, struct machine *machine)
> >  		dso->has_build_id = true;
> >  }
> >  
> > -static struct dso *machine__create_kernel(struct machine *machine)
> > +static struct dso *machine__get_kernel(struct machine *machine)
> >  {
> >  	const char *vmlinux_name = NULL;
> >  	struct dso *kernel;
> >  
> >  	if (machine__is_host(machine)) {
> >  		vmlinux_name = symbol_conf.vmlinux_name;
> > -		kernel = dso__new_kernel(vmlinux_name);
> > +		if (!vmlinux_name)
> > +			vmlinux_name = "[kernel.kallsyms]";
> > +
> > +		kernel = dso__kernel_findnew(machine, vmlinux_name,
> > +					     "[kernel]",
> > +					     DSO_TYPE_KERNEL);
> >  	} else {
> > +		char bf[PATH_MAX];
> > +
> >  		if (machine__is_default_guest(machine))
> >  			vmlinux_name = symbol_conf.default_guest_vmlinux_name;
> > -		kernel = dso__new_guest_kernel(machine, vmlinux_name);
> > +		if (!vmlinux_name)
> > +			vmlinux_name = machine__mmap_name(machine, bf,
> > +							  sizeof(bf));
> > +
> > +		kernel = dso__kernel_findnew(machine, vmlinux_name,
> > +					     "[guest.kernel]",
> > +					     DSO_TYPE_GUEST_KERNEL);
> >  	}
> >  
> > -	if (kernel != NULL) {
> > +	if (kernel != NULL && (!kernel->has_build_id))
> >  		dso__read_running_kernel_build_id(kernel, machine);
> > -		dsos__add(&machine->kernel_dsos, kernel);
> > -	}
> > +
> >  	return kernel;
> >  }
> >  
> > @@ -2329,7 +2336,7 @@ void machine__destroy_kernel_maps(struct machine *machine)
> >  
> >  int machine__create_kernel_maps(struct machine *machine)
> >  {
> > -	struct dso *kernel = machine__create_kernel(machine);
> > +	struct dso *kernel = machine__get_kernel(machine);
> >  
> >  	if (kernel == NULL ||
> >  	    __machine__create_kernel_maps(machine, kernel) < 0)
> > diff --git a/tools/perf/util/symbol.h b/tools/perf/util/symbol.h
> > index 325ee36..4f377d9 100644
> > --- a/tools/perf/util/symbol.h
> > +++ b/tools/perf/util/symbol.h
> > @@ -155,7 +155,6 @@ struct dso {
> >  };
> >  
> >  struct dso *dso__new(const char *name);
> > -struct dso *dso__new_kernel(const char *name);
> >  void dso__delete(struct dso *dso);
> >  
> >  int dso__name_len(const struct dso *dso);
> > -- 
> > 1.7.1
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