Re: [PATCH dwarves 0/2] dwarf_loader: improve cus__merging_cu()

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On Tue, Apr 6, 2021 at 11:03 AM Arnaldo Carvalho de Melo
<arnaldo.melo@xxxxxxxxx> wrote:
>
> Em Tue, Apr 06, 2021 at 10:48:22AM -0700, Yonghong Song escreveu:
> >
> >
> > On 4/6/21 10:23 AM, Yonghong Song wrote:
> > >
> > >
> > > On 4/6/21 10:03 AM, Arnaldo Carvalho de Melo wrote:
> > > > Em Tue, Apr 06, 2021 at 01:59:30PM -0300, Arnaldo Carvalho de Melo
> > > > escreveu:
> > > > > Em Tue, Apr 06, 2021 at 01:55:54PM -0300, Arnaldo Carvalho de
> > > > > Melo escreveu:
> > > > > > Em Tue, Apr 06, 2021 at 01:40:20PM -0300, Arnaldo Carvalho
> > > > > > de Melo escreveu:
> > > > > > > Em Tue, Apr 06, 2021 at 10:22:37AM -0300, Arnaldo
> > > > > > > Carvalho de Melo escreveu:
> > > > > > > > I'm seeing these here:
> > > > > >
> > > > > > > > [acme@five bpf]$ rm -f ../build/bpf_clang_thin_lto/*vmlinu*
> > > > > > > > [acme@five bpf]$ time make -j28 LLVM=1 LLVM_IAS=1
> > > > > > > > O=../build/bpf_clang_thin_lto/ vmlinux
> > > > > > > > make[1]: Entering directory '/home/acme/git/build/bpf_clang_thin_lto'
> > > > > > > >    GEN     Makefile
> > > > > > > >    DESCEND  objtool
> > > > > > > >    DESCEND  bpf/resolve_btfids
> > > > > > > >    CALL    /home/acme/git/bpf/scripts/atomic/check-atomics.sh
> > > > > > > >    CALL    /home/acme/git/bpf/scripts/checksyscalls.sh
> > > > > > > >    CHK     include/generated/compile.h
> > > > > > > >    GEN     .version
> > > > > > > >    CHK     include/generated/compile.h
> > > > > > > >    UPD     include/generated/compile.h
> > > > > > > >    CC      init/version.o
> > > > > > > >    AR      init/built-in.a
> > > > > > > >    GEN     .tmp_initcalls.lds
> > > > > > > >    LTO     vmlinux.o
> > > > > > > >    OBJTOOL vmlinux.o
> > > > > > > > vmlinux.o: warning: objtool:
> > > > > > > > aesni_gcm_init_avx_gen2()+0x12: unsupported stack
> > > > > > > > pointer realignment
> > > > > > > > vmlinux.o: warning: objtool:
> > > > > > > > aesni_gcm_enc_update_avx_gen2()+0x12: unsupported
> > > > > > > > stack pointer realignment
> > > > > > > > vmlinux.o: warning: objtool:
> > > > > > > > aesni_gcm_dec_update_avx_gen2()+0x12: unsupported
> > > > > > > > stack pointer realignment
> > > > > > > > vmlinux.o: warning: objtool:
> > > > > > > > aesni_gcm_finalize_avx_gen2()+0x12: unsupported
> > > > > > > > stack pointer realignment
> > > > > > > > vmlinux.o: warning: objtool:
> > > > > > > > aesni_gcm_init_avx_gen4()+0x12: unsupported stack
> > > > > > > > pointer realignment
> > > > > > > > vmlinux.o: warning: objtool:
> > > > > > > > aesni_gcm_enc_update_avx_gen4()+0x12: unsupported
> > > > > > > > stack pointer realignment
> > > > > > > > vmlinux.o: warning: objtool:
> > > > > > > > aesni_gcm_dec_update_avx_gen4()+0x12: unsupported
> > > > > > > > stack pointer realignment
> > > > > > > > vmlinux.o: warning: objtool:
> > > > > > > > aesni_gcm_finalize_avx_gen4()+0x12: unsupported
> > > > > > > > stack pointer realignment
> > > > > > > >    MODPOST vmlinux.symvers
> > > > > > > >    MODINFO modules.builtin.modinfo
> > > > > > > >    GEN     modules.builtin
> > > > > > > >    LD      .tmp_vmlinux.btf
> > > > > > > >    BTF     .btf.vmlinux.bin.o
> > > > > > > >    LD      .tmp_vmlinux.kallsyms1
> > > > > > > >    KSYMS   .tmp_vmlinux.kallsyms1.S
> > > > > > > >    AS      .tmp_vmlinux.kallsyms1.S
> > > > > > > >    LD      .tmp_vmlinux.kallsyms2
> > > > > > > >    KSYMS   .tmp_vmlinux.kallsyms2.S
> > > > > > > >    AS      .tmp_vmlinux.kallsyms2.S
> > > > > > > >    LD      vmlinux
> > > > > > > >    BTFIDS  vmlinux
> > > > > > > > WARN: multiple IDs found for 'inode': 232, 28822 - using 232
> > > > > > > > WARN: multiple IDs found for 'file': 374, 28855 - using 374
> > > > > > > > WARN: multiple IDs found for 'path': 379, 28856 - using 379
> > > > > > > > WARN: multiple IDs found for 'vm_area_struct': 177, 28929 - using 177
> > > > > > > > WARN: multiple IDs found for 'task_struct': 97, 28966 - using 97
> > > > > > > > WARN: multiple IDs found for 'seq_file': 510, 29059 - using 510
> > > > > > > > WARN: multiple IDs found for 'inode': 232, 29345 - using 232
> > > > > > > > WARN: multiple IDs found for 'file': 374, 29429 - using 374
> > > > > > > > WARN: multiple IDs found for 'path': 379, 29430 - using 379
> > > > > > > > WARN: multiple IDs found for 'vm_area_struct': 177, 29471 - using 177
> > > > > > > > WARN: multiple IDs found for 'task_struct': 97, 29481 - using 97
> > > > > > > > WARN: multiple IDs found for 'seq_file': 510, 29512 - using 510
> > > > > > > >    SORTTAB vmlinux
> > > > > > > >    SYSMAP  System.map
> > > > > > > > make[1]: Leaving directory '/home/acme/git/build/bpf_clang_thin_lto'
> > > > > > > >
> > > > > > > > [acme@five pahole]$ clang -v
> > > > > > > > clang version 11.0.0 (Fedora 11.0.0-2.fc33)
> > >
> > > This could be due to the compiler. The clang 11 is used here. Sedat is
> > > using clang 12 and didn't see warnings and I am using clang dev branch
> > > (clang 13) and didn't see warnings either. clang 11 could generate
> > > some debuginfo where pahole didn't handle it properly.
> > >
> > > I tried to build locally with clang 11 but it crashed as I enabled
> > > assert during compiler build. Will try a little bit more.
> >
> > Yes, I can see it with llvm11:
> >
> >   LD      vmlinux
> >
> >
> >   BTFIDS  vmlinux
> >
> >
> > WARN: multiple IDs found for 'inode': 245, 36255 - using 245
> >
> >
> > WARN: multiple IDs found for 'file': 390, 36288 - using 390
> >
> >
> > WARN: multiple IDs found for 'path': 395, 36289 - using 395
> >
> >
> > WARN: multiple IDs found for 'vm_area_struct': 190, 36362 - using 190
> >
> >
> > WARN: multiple IDs found for 'task_struct': 93, 36399 - using 93
> >
> >
> > WARN: multiple IDs found for 'seq_file': 524, 36498 - using 524
> >
> >
> > WARN: multiple IDs found for 'inode': 245, 36784 - using 245
> >
> >
> > WARN: multiple IDs found for 'file': 390, 36868 - using 390
> >
> >
> > WARN: multiple IDs found for 'path': 395, 36869 - using 395
> >
> >
> > WARN: multiple IDs found for 'vm_area_struct': 190, 36910 - using 190
> >
> >
> > WARN: multiple IDs found for 'task_struct': 93, 36920 - using 93
> >
> >
> > WARN: multiple IDs found for 'seq_file': 524, 36951 - using 524
> >
> >
> >   SORTTAB vmlinux
> >
> >
> >   SYSMAP  System.map
> >
> >
> >   LTO [M] crypto/crypto_engine.lto.o
> >
> >
> >   LTO [M] drivers/crypto/virtio/virtio_crypto.lto.o
> >
> > $ clang --version
> > clang version 11.1.0 (https://github.com/llvm/llvm-project.git
> > 1fdec59bffc11ae37eb51a1b9869f0696bfd5312)
> > Target: x86_64-unknown-linux-gnu
> > Thread model: posix
> > InstalledDir: /home/yhs/work/llvm-project/llvm/build/install/bin
> >
> > clang12 is okay:
> >
> >   LTO     vmlinux.o
> >   OBJTOOL vmlinux.o
> >   MODPOST vmlinux.symvers
> >   MODINFO modules.builtin.modinfo
> >   GEN     modules.builtin
> >   LD      .tmp_vmlinux.btf
> >   BTF     .btf.vmlinux.bin.o
> >   LD      .tmp_vmlinux.kallsyms1
> >   KSYMS   .tmp_vmlinux.kallsyms1.S
> >   AS      .tmp_vmlinux.kallsyms1.S
> >   LD      .tmp_vmlinux.kallsyms2
> >   KSYMS   .tmp_vmlinux.kallsyms2.S
> >
> > $ clang --version
> > clang version 12.0.0 (https://github.com/llvm/llvm-project.git
> > 31001be371e8f2c74470e727e54503fb2aabec8b)
> > Target: x86_64-unknown-linux-gnu
> > Thread model: posix
> > InstalledDir: /home/yhs/work/llvm-project/llvm/build/install/bin
> >
> > I think we do not need to fix pahole for llvm11.
> > When linus tree 5.12 is out. clang 12 should have been released
> > or very close, we can just recommend clang 12 and later.
>
> Agreed, and it is just for _thin_ LTO, those warnings don't pop up when
> building for full LTO with clang 11, the one in Fedora 33.
>
> And Fedora 34 beta has clang/llvm 12.0, so we're good.
>
> /me goes back to building clang/llvm HEAD, reducing the number of linker
> instances to 1 as I have just 32GB of ram in this Ryzen machine... ;-)

32GB should be enough for a lot of parallel links - unless you're
using ld.bfd - highly advised to switch to gold or lld & then you
shuold be able to do a fair number of parallel links without loads of
thrashing.

 https://llvm.org/docs/GettingStarted.html#common-problems discusses a
few things to try

 - Dave



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