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Message-ID: <20110617123856.GB2699@jolsa.brq.redhat.com>
Date: Fri, 17 Jun 2011 14:38:56 +0200
From: Jiri Olsa <jolsa@...hat.com>
To: acme@...hat.com
Cc: fweisbec@...il.com, yanmin_zhang@...ux.intel.com, avi@...hat.com,
mingo@...e.hu, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] perf, report: use properly build_id kernel binaries
hi, any feedback?
thanks,
jirka
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@...hat.com>
> ---
> 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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