[Buildroot] [PATCH 6/6] linux/perf: build the host perf tool
Thomas Petazzoni
thomas.petazzoni at free-electrons.com
Sat Mar 19 13:55:15 UTC 2016
Yann,
On Fri, 11 Mar 2016 19:19:59 +0100, Yann E. MORIN wrote:
> Currently, we only build the target variant of the perf tool. However,
> perf on the target may generate a bunch of data files that may have to
> be analysed on the host.
>
> There is no host-variant of the linux-tools infrastructure, so we just
> build the host perf at the same time we build the target one.
>
> Signed-off-by: "Yann E. MORIN" <yann.morin.1998 at free.fr>
> Cc: Thomas De Schampheleire <patrickdepinguin at gmail.com>
First of all, I have to say I hate this target package that builds and
installs host stuff. But, since I don't have a better solution to
offer, and it's anyway not the only package in this case (qt/qt5 are
also target packages, and they install stuff in host), I'm fine with
the general approach.
I have some comments about the details, though.
> ---
> linux/Config.tools.in | 4 ++++
> linux/linux-tool-perf.mk | 51 ++++++++++++++++++++++++++++++++++++++++++------
> 2 files changed, 49 insertions(+), 6 deletions(-)
>
> diff --git a/linux/Config.tools.in b/linux/Config.tools.in
> index 24ef8cd..a01b53e 100644
> --- a/linux/Config.tools.in
> +++ b/linux/Config.tools.in
> @@ -26,4 +26,8 @@ config BR2_LINUX_KERNEL_TOOL_PERF
>
> https://perf.wiki.kernel.org/
>
> +config BR2_LINUX_KERNEL_TOOL_HOST_PERF
> + bool "host-perf"
> + depends on BR2_LINUX_KERNEL_TOOL_PERF
Indentation should just tab.
> +# For the host, we inherit the same flags as for the target,
> +# overriding just those that are needed.
I don't really understand this, it seems really weird to me, and I
would find it much more future proof to have separate target and host
flags. Otherwise, any addition of a flag to the target variant can
break in subtle way the host variant.
> +HOST_PERF_MAKE_FLAGS = \
> + $(PERF_MAKE_FLAGS) \
> + CFLAGS="$(HOST_CFLAGS) -I$(HOST_DIR)/usr/include/elfutils" \
We don't have this -I for the target variant. Why do we need it for the
host variant?
> + LDFLAGS="$(HOST_LDFLAGS)" \
> + LD="$(HOSTLD)" \
> + ARCH=$(PERF_ARCH) \
> + CROSS_COMPILE= \
> + DESTDIR=$(HOST_DIR)
> +
> +# No host-packages in Buildroot, but we don't let it depend on the
> +# libraries provided by the host system (they may be there or not,
> +# depending on the user's system, but we won't play that game).
This sentence is not really clear IMO. What about:
# For the following optional dependencies of perf, Buildroot doesn't
# provide any host package, and we don't want to rely on those
# libraries being provided by the host system.
> +HOST_PERF_MAKE_FLAGS += \
> + NO_SLANG=1 \
> + NO_LIBUNWIND=1 \
> + NO_LIBNUMA=1 \
> + NO_LIBELF=1 NO_DWARF=1
> +
> # The call to backtrace() function fails for ARC, because for some
> # reason the unwinder from libgcc returns early. Thus the usage of
> # backtrace() should be disabled in perf explicitly: at build time
> @@ -49,6 +69,7 @@ endif
> # instead of the complete backtrace.
> ifeq ($(BR2_arc),y)
> PERF_MAKE_FLAGS += NO_BACKTRACE=1
> +HOST_PERF_MAKE_FLAGS += NO_BACKTRACE=1
Why ?
> endif
>
> ifeq ($(BR2_PACKAGE_SLANG),y)
> @@ -76,14 +97,14 @@ PERF_MAKE_FLAGS += NO_LIBELF=1 NO_DWARF=1
> endif
>
> ifeq ($(BR2_PACKAGE_ZLIB),y)
> -PERF_DEPENDENCIES += zlib
> +PERF_DEPENDENCIES += zlib host-zlib
This is the part I'm really not a big fan of. You enable a target
package, and it affects the configuration of a host package. Not nice.
Is there an actual connection between zlib/xz support in the target
perf and the need to have it in host-perf? Like is zlib/xz support used
to compress the data output by the target perf, which needs to be
uncompressed by the host perf ?
Thanks!
Thomas
--
Thomas Petazzoni, CTO, Free Electrons
Embedded Linux, Kernel and Android engineering
http://free-electrons.com
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