Re: [PATCH bpf-next v4] selftests/bpf: use auto-dependencies for test objects

Andrii Nakryiko
2024-07-19T22:25:53Z

On Fri, Jul 19, 2024 at 2:54 PM Tony Ambardar <tony.ambardar@gmail.com> wrote:
>
> On Fri, Jul 19, 2024 at 11:18:16AM -0700, Andrii Nakryiko wrote:
> > On Thu, Jul 18, 2024 at 3:57 PM Ihor Solodrai <ihor.solodrai@pm.me> wrote:
> > >
> > > Make use of -M compiler options when building .test.o objects to
> > > generate .d files and avoid re-building all tests every time.
> > >
> > > Previously, if a single test bpf program under selftests/bpf/progs/*.c
> > > has changed, make would rebuild all the *.bpf.o, *.skel.h and *.test.o
> > > objects, which is a lot of unnecessary work.
> > >
> > > A typical dependency chain is:
> > > progs/x.c -> x.bpf.o -> x.skel.h -> x.test.o -> trunner_binary
> > >
> > > However for many tests it's not a 1:1 mapping by name, and so far
> > > %.test.o have been simply dependent on all %.skel.h files, and
> > > %.skel.h files on all %.bpf.o objects.
> > >
> > > Avoid full rebuilds by instructing the compiler (via -MMD) to
> > > produce *.d files with real dependencies, and appropriately including
> > > them. Exploit make feature that rebuilds included makefiles if they
> > > were changed by setting %.test.d as prerequisite for %.test.o files.
> > >
> > > A couple of examples of compilation time speedup (after the first
> > > clean build):
> > >
> > > $ touch progs/verifier_and.c && time make -j8
> > > Before: real 0m16.651s
> > > After: real 0m2.245s
> > > $ touch progs/read_vsyscall.c && time make -j8
> > > Before: real 0m15.743s
> > > After: real 0m1.575s
> > >
> > > A drawback of this change is that now there is an overhead due to make
> > > processing lots of .d files, which potentially may slow down unrelated
> > > targets. However a time to make all from scratch hasn't changed
> > > significantly:
> > >
> > > $ make clean && time make -j8
> > > Before: real 1m31.148s
> > > After: real 1m30.309s
> > >
> > > Suggested-by: Eduard Zingerman <eddyz87@gmail.com>
> > > Signed-off-by: Ihor Solodrai <ihor.solodrai@pm.me>
> > >
> > > ---
> > > v3 -> v4: Make $(TRUNNER_BPF_OBJS) order only prereq of trunner binary
> > > v2 -> v3: Restore dependency on $(TRUNNER_BPF_OBJS)
> > > v1 -> v2: Make %.test.d prerequisite order only
> > > ---
> > > tools/testing/selftests/bpf/.gitignore | 1 +
> > > tools/testing/selftests/bpf/Makefile | 44 +++++++++++++++++++-------
> > > 2 files changed, 34 insertions(+), 11 deletions(-)
> > >
> >
> > It seems to behave correctly, but it reports wrong flavor when
> > building .bpf.o, e.g.,:
> >
> Hi Andrii,
>
> This is actually an old, confusing bug unrelated to the current (very
> nice) improvements. I have a fix as part of a larger series
> targeting libc portability and MIPS support which I'll post shortly. Or
> I can send separately if you like?

Please send it separately, having small targeted Makefile changes
makes it much easier to test, review, and land them quickly.

>
> Thanks,
> Tony
>
> > $ touch progs/test_vmlinux.c
> > $ make -j90
> > CLNG-BPF [test_maps] test_vmlinux.bpf.o
> > CLNG-BPF [test_maps] test_vmlinux.bpf.o
> > CLNG-BPF [test_maps] test_vmlinux.bpf.o
> > GEN-SKEL [test_progs] test_vmlinux.skel.h
> > GEN-SKEL [test_progs-cpuv4] test_vmlinux.skel.h
> > GEN-SKEL [test_progs-no_alu32] test_vmlinux.skel.h
> > TEST-OBJ [test_progs] vmlinux.test.o
> > TEST-OBJ [test_progs-no_alu32] vmlinux.test.o
> > EXT-COPY [test_progs-no_alu32] urandom_read bpf_testmod.ko
> > bpf_test_no_cfi.ko liburandom_read.so xdp_synproxy sign-file
> > uprobe_multi ima_setup.sh verify_sig_setup.sh
> > btf_dump_test_case_bitfields.c btf_dump_test_case_multidim.c
> > btf_dump_test_case_namespacing.c btf_dump_test_case_ordering.c
> > btf_dump_test_case_packing.c btf_dump_test_case_padding.c
> > btf_dump_test_case_syntax.c
> > TEST-OBJ [test_progs-cpuv4] vmlinux.test.o
> > EXT-COPY [test_progs-cpuv4] urandom_read bpf_testmod.ko
> > bpf_test_no_cfi.ko liburandom_read.so xdp_synproxy sign-file
> > uprobe_multi ima_setup.sh verify_sig_setup.sh
> > btf_dump_test_case_bitfields.c btf_dump_test_case_multidim.c
> > btf_dump_test_case_namespacing.c btf_dump_test_case_ordering.c
> > btf_dump_test_case_packing.c btf_dump_test_case_padding.c
> > btf_dump_test_case_syntax.c
> > make[1]: Nothing to be done for 'docs'.
> > BINARY test_progs
> > BINARY test_progs-no_alu32
> > BINARY test_progs-cpuv4
> > $ ls -la test_vmlinux.bpf.o no_alu32/test_vmlinux.bpf.o cpuv4/test_vmlinux.bpf.o
> > -rw-r--r-- 1 andriin users 21344 Jul 19 11:08 cpuv4/test_vmlinux.bpf.o
> > -rw-r--r-- 1 andriin users 21408 Jul 19 11:08 no_alu32/test_vmlinux.bpf.o
> > -rw-r--r-- 1 andriin users 21408 Jul 19 11:08 test_vmlinux.bpf.o
> >
> >
> > Note [test_maps] for all three variants (I expected
> > test_maps/test_progs + no_alu32 + cpuv4, just like we see for skel.h).
> > Can you please double check what's going on? Looking at timestamps it
> > seems like they are actually regenerated, though.
> >
> >
> > BTW, if you get a chance, see if you can avoid unnecessary EXT-COPY as
> > well (probably a bit smarter rule dependency should be set up, e.g.,
> > phony target that then depends on actual files or something like
> > that).
> >
> > Regardless, this is a massive improvement and seems to work correctly,
> > so I've applied this and will wait for follow ups. Thanks a lot!
> >
> > BTW, are you planning to look into vmlinux.h optimization as well?
> >
> > > diff --git a/tools/testing/selftests/bpf/.gitignore b/tools/testing/selftests/bpf/.gitignore
> > > index 5025401323af..4e4aae8aa7ec 100644
> > > --- a/tools/testing/selftests/bpf/.gitignore
> > > +++ b/tools/testing/selftests/bpf/.gitignore
> > > @@ -31,6 +31,7 @@ test_tcp_check_syncookie_user
> > > test_sysctl
> > > xdping
> > > test_cpp
> > > +*.d
> > > *.subskel.h
> > > *.skel.h
> > > *.lskel.h
> >
> > …