On Thu, Mar 23, 2023 at 6:27 AM Arnaldo Carvalho de Melo <acme@xxxxxxxxxx> wrote: > > Em Thu, Mar 23, 2023 at 09:54:37AM +1100, Stephen Rothwell escreveu: > > Hi Ian, > > > > On Wed, 22 Mar 2023 11:37:31 -0700 Ian Rogers <irogers@xxxxxxxxxx> wrote: > > > > > > On Tue, Mar 21, 2023 at 2:40 PM Stephen Rothwell <sfr@xxxxxxxxxxxxxxxx> wrote: > > > > > > > > Hi all, > > > > > > > > On Fri, 17 Mar 2023 09:50:25 +1100 Stephen Rothwell <sfr@xxxxxxxxxxxxxxxx> wrote: > > > > > > > > > > After merging the perf tree, today's linux-next build (native perf) > > > > > failed like this: > > > > > > > > > > Auto-detecting system features: > > > > > ... clang-bpf-co-re: [ [32mon [m ] > > > > > ... llvm: [ [31mOFF [m ] > > > > > ... libcap: [ [32mon [m ] > > > > > ... libbfd: [ [32mon [m ] > > > > > > > > > > make[1]: *** Deleting file '/home/sfr/next/perf/util/bpf_skel/vmlinux.h' > > > > > libbpf: failed to find '.BTF' ELF section in /boot/vmlinux-6.0.0-5-powerpc64le > > > > > Error: failed to load BTF from /boot/vmlinux-6.0.0-5-powerpc64le: No data available > > > > > make[1]: *** [Makefile.perf:1075: /home/sfr/next/perf/util/bpf_skel/vmlinux.h] Error 195 > > > > > make[1]: *** Waiting for unfinished jobs.... > > > > > make: *** [Makefile.perf:236: sub-make] Error 2 > > > > > Command exited with non-zero status 2 > > > > > > > > > > To be clear this is a native build of perf on a PPC64le host using this > > > > > command line: > > > > > > > > > > make -C tools/perf -f Makefile.perf -s -O -j60 O=../perf EXTRA_CFLAGS=-Wno-psabi > > > > > > > > > > (I could probably remove the EXTRA_CLFAGS now that I am building with > > > > > gcc 12.2) > > > > > > > > > > I don't know which commit caused this. > > > > > > > > > > I have used the perf tree from next-20230316 for today. > > > > > > > > I am still getting this build failure. > > > > The build failure is intentional as not having BPF skeleton support in > > > the perf tool will remove features. I've just sent: > > > https://lore.kernel.org/lkml/20230322183108.1380882-1-irogers@xxxxxxxxxx/ > > > Which will recommend adding NO_BPF_SKEL=1 to your build options when > > > this failure occurs. I didn't think a features test was appropriate > > > for this as the feature test would basically replicate the vmlinux.h > > > generation and I didn't want to move that support through the build > > > system. > > > I was trying to understand why this step fails, but from the error > > messages, it seems to require something to be present in the distro > > supplied kernel image? Is there something missing from the ppc > > build process? Or toolchain? Why is it looking at the installed > > kernel and not the built kernel? Does the perf build now depend on the > > kernel being built first? > > > > I will add NO_BPF_SKEL=1 to my build from tomorrow, but surely that > > means that we miss some perf build testing :-( > > Before this BUILD_BPF_SKEL wasn't on by default, so you're back testing > as much as before. > > Having said that, we need to improve the warning and I processed a patch > from Ian to that extent: > > https://git.kernel.org/pub/scm/linux/kernel/git/acme/linux.git/commit/?h=tmp.perf-tools-next&id=12a83df53444165d39d3e09fcd9627e7bec7828e > > $(SKEL_OUT)/vmlinux.h: $(VMLINUX_BTF) $(BPFTOOL) > ifeq ($(VMLINUX_H),) > - $(QUIET_GEN)$(BPFTOOL) btf dump file $< format c > $@ > + $(QUIET_GEN)$(BPFTOOL) btf dump file $< format c > $@ || \ > + (echo "Failure to generate vmlinux.h needed for the recommended BPF skeleton support." && \ > + echo "To disable this use the build option NO_BPF_SKEL=1." && \ > + echo "Alternatively point at a pre-generated vmlinux.h with VMLINUX_H=<path>." && \ > + false) > else > $(Q)cp "$(VMLINUX_H)" $@ > endif > > Which improves a bit the situation. > > We could check if bpftool is available and if not, suggest installing > it. > > If it is available, we could check if /sys/kernel/bpf/ is available, if > not suggest using a kernel with CONFIG_DEBUG_INFO_BTF=y, as most distros > have by now. > > As to the features this enables: > > ⬢[acme@toolbox perf-tools-next]$ ls -la tools/perf/util/bpf_skel/*.c > -rw-r--r--. 1 acme acme 5581 Oct 17 09:07 tools/perf/util/bpf_skel/bperf_cgroup.bpf.c > -rw-r--r--. 1 acme acme 1764 May 5 2022 tools/perf/util/bpf_skel/bperf_follower.bpf.c > -rw-r--r--. 1 acme acme 1438 May 5 2022 tools/perf/util/bpf_skel/bperf_leader.bpf.c > -rw-r--r--. 1 acme acme 2290 May 5 2022 tools/perf/util/bpf_skel/bpf_prog_profiler.bpf.c > -rw-r--r--. 1 acme acme 2164 May 5 2022 tools/perf/util/bpf_skel/func_latency.bpf.c > -rw-r--r--. 1 acme acme 9017 Aug 26 2022 tools/perf/util/bpf_skel/kwork_trace.bpf.c > -rw-r--r--. 1 acme acme 9251 Mar 14 08:33 tools/perf/util/bpf_skel/lock_contention.bpf.c > -rw-r--r--. 1 acme acme 6109 Feb 27 17:47 tools/perf/util/bpf_skel/off_cpu.bpf.c > -rw-r--r--. 1 acme acme 4310 Mar 15 11:08 tools/perf/util/bpf_skel/sample_filter.bpf.c > ⬢[acme@toolbox perf-tools-next]$ > > For instance, take a look at these csets: > > ⬢[acme@toolbox perf-tools-next]$ git log --oneline tools/perf/util/bpf_skel/lock_contention.bpf.c > d24c0144b1dde00f perf lock contention: Show per-cpu rq_lock with address > 1811e82767dcc6eb perf lock contention: Track and show siglock with address > 3ace2435bb93445e perf lock contention: Track and show mmap_lock with address > 17535a33a9c1e4fb perf lock contention: Fix compiler builtin detection > 1bece1351c653c3d perf lock contention: Support old rw_semaphore type > 3477f079fe70b3c9 perf lock contention: Add -o/--lock-owner option > ebab291641bed48f perf lock contention: Support filters for different aggregation > 5e3febe7b7b99f94 perf lock contention: Support lock addr/name filtering for BPF > 529772c4df286159 perf lock contention: Support lock type filtering for BPF > 688d2e8de231c54e perf lock contention: Add -l/--lock-addr option > eca949b2b4addd94 perf lock contention: Implement -t/--threads option for BPF > fd507d3e359c7e06 perf lock contention: Add lock_data.h for common data > c66a36af7ba3a628 perf lock contention: Do not use BPF task local storage > 433b31fa00797a2a perf lock contention: Fix a build error on 32-bit > c1da8dd5c11dabd5 perf lock contention: Skip stack trace from BPF > 6d499a6b3d90277d perf lock: Print the number of lost entries for BPF > 6fda2405f414b24a perf lock: Implement cpu and task filters for BPF > 407b36f69efbdccf perf lock: Use BPF for lock contention analysis > ⬢[acme@toolbox perf-tools-next]$ > > > or: > > ⬢[acme@toolbox perf-tools-next]$ git log --oneline tools/perf/util/bpf_skel/kwork_trace.bpf.c > acfb65fe1d11a97f perf kwork: Add workqueue trace BPF support > 5a81927a407c050a perf kwork: Add softirq trace BPF support > 420298aefe94840f perf kwork: Add IRQ trace BPF support > daf07d220710a3c8 perf kwork: Implement BPF trace > ⬢[acme@toolbox perf-tools-next]$ > > So we need to fine tune this detection of needed components to build > these features, in time for the v6.4 merge window, that is why we > decided to make this opt-out to hammer out problems. > > Other arches probably will hit some of these problems, lets try to > encourage others to try what is in linux-next. Just to throw out, perhaps we could ship a vmlinux.h in the perf source tree. We could also validate it with something similar to the header file checking. This would remove the bpftool and properly built kernel issues. It may make a package maintainer's life easier. Thanks, Ian > - Arnaldo
