On Thu, Aug 4, 2022 at 5:12 AM Owen Rafferty <owen@xxxxxxxxxxxxxxxx> wrote:
>
> On 22/08/03 12:40PM, Masahiro Yamada wrote:
> > On Wed, Aug 3, 2022 at 3:49 AM Owen Rafferty <owen@xxxxxxxxxxxxxxxx> wrote:
> > >
> > > Remove the bash build dependency for those who otherwise do not have it
> > > installed. This should also provide a slight speedup.
> >
> > I do not know if this is worth the effort,
> > but do you have any benchmark on how fast it is?
>
> To be clear, I'm not asking for every single bash script in the tree to be
> rewritten in posix shell -- it was only this script that made bash a hard
> dependency (on x86 at least).
>
> For a configuration suitable for my system w/ 4 HT cores:
>
> bash
> real8m 47.79s user54m 30.91s sys13m 56.88s
>
> sh (dash)
> real7m 34.94s user46m 42.63s sys11m 54.02s
You need to explain what command you measured.
But, never mind. I did it by myself.
With x86_64 defconfig build, I got 2824 objects.
$ find . -name "*.o" | grep -v vmlinux | wc
2824 2824 78929
Without your patch,
$ export NM=nm
$ time sh -c 'find . -name "*.o" | grep -v vmlinux | xargs -n1
./scripts/check-local-export'
real 0m58.816s
user 0m30.772s
sys 0m31.420s
With your patch
$ export NM=nm
$ time sh -c 'find . -name "*.o" | grep -v vmlinux | xargs -n1
./scripts/check-local-export'
real 8m22.922s
user 7m53.015s
sys 0m30.147s
So, it is the opposite.
Your patch makes the code extremely slow.
More than 8x slower.
+ type="${symbol_types##* $name,}"
+ type="${type%% *}"
This code is really slow.
> > > -# the changes made to 'symbol_types' and 'export_symbols' would be lost.
> > > -shopt -s lastpipe
> > > -
> > > -declare -A symbol_types
> > > -declare -a export_symbols
> > > +symbol_types=""
> > > +export_symbols=""
> > >
> > > exit_code=0
> > >
> > > -# If there is no symbol in the object, ${NM} (both GNU nm and llvm-nm) shows
> > > -# 'no symbols' diagnostic (but exits with 0). It is harmless and hidden by
> > > -# '2>/dev/null'. However, it suppresses real error messages as well. Add a
> > > -# hand-crafted error message here.
> > > -#
> > > -# TODO:
> > > -# Use --quiet instead of 2>/dev/null when we upgrade the minimum version of
> > > -# binutils to 2.37, llvm to 13.0.0.
> > > -# Then, the following line will be really simple:
> > > -# ${NM} --quiet ${1} |
> > > -
> > > -{ ${NM} ${1} 2>/dev/null || { echo "${0}: ${NM} failed" >&2; false; } } |
> > > while read value type name
> > > do
> > > # Skip the line if the number of fields is less than 3.
> > > @@ -46,26 +26,40 @@ do
> > > # case 2)
> > > # For Clang LTO, llvm-nm outputs a line with type 't' but empty name:
> > > # "---------------- t"
> > > - if [[ -z ${name} ]]; then
> > > + if [ -z ${name} ]; then
> > > continue
> > > fi
> > >
> > > - # save (name, type) in the associative array
> > > - symbol_types[${name}]=${type}
> > > + # save (name, type) in "associative array"
> > > + symbol_types="$symbol_types ${name},${type}"
> > >
> > > # append the exported symbol to the array
> > > - if [[ ${name} == __ksymtab_* ]]; then
> > > - export_symbols+=(${name#__ksymtab_})
> > > - fi
> > > -done
> > > + case ${name} in __ksymtab_*)
> > > + export_symbols="$export_symbols ${name#__ksymtab_}"
> > > + esac
> > >
> > > -for name in "${export_symbols[@]}"
> > > +# If there is no symbol in the object, ${NM} (both GNU nm and llvm-nm) shows
> > > +# 'no symbols' diagnostic (but exits with 0). It is harmless and hidden by
> > > +# '2>/dev/null'. However, it suppresses real error messages as well. Add a
> > > +# hand-crafted error message here.
> > > +#
> > > +# TODO:
> > > +# Use --quiet instead of 2>/dev/null when we upgrade the minimum version of
> > > +# binutils to 2.37, llvm to 13.0.0.
> > > +# Then, the following line will be simple:
> > > +# $(${NM} --quiet ${1} || kill -INT $$)
> > > +done <<EOF
> > > +$( ${NM} ${1} 2>/dev/null || { echo "${0}: ${NM} failed" >&2; kill -INT $$; })
> > > +EOF
> > > +
> > > +for name in $export_symbols
> > > do
> > > - # nm(3) says "If lowercase, the symbol is usually local"
> > > - if [[ ${symbol_types[$name]} =~ [a-z] ]]; then
> > > + type="${symbol_types##* $name,}"
> > > + type="${type%% *}"
> > > + case ${type} in [a-z])
> > > echo "$@: error: local symbol '${name}' was exported" >&2
> > > exit_code=1
> > > - fi
> > > + esac
> > > done
> > >
> > > exit ${exit_code}
> > > --
> > > 2.37.1
> > >
> >
> >
> > --
> > Best Regards
> > Masahiro Yamada
--
Best Regards
Masahiro Yamada
