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kbuild: speed up checksyscalls.sh

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checksyscalls.sh is run at every "make" run while building the kernel,
even if no files have changed. I looked at where we spend time in
a trivial empty rebuild and found checksyscalls.sh to be a source
of noticeable overhead, as it spawns a lot of child processes just
to call 'cat' copying from stdin to stdout, once for each of the
over 400 x86 syscalls.

Using a shell-builtin (echo) instead of the external command gives
us a 13x speedup:

    Before		   After
real	0m1.018s       real	0m0.077s
user	0m0.068s       user	0m0.048s
sys	0m0.156s       sys	0m0.024s

The time it took to rebuild a single file on my machine dropped
from 5.5 seconds to 4.5 seconds.

Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
This commit is contained in:
Arnd Bergmann 2017-06-01 16:57:07 +02:00 committed by Masahiro Yamada
parent 6f0fa58e45
commit d21832e212
1 changed files with 4 additions and 7 deletions
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11
scripts/checksyscalls.sh
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@ -202,15 +202,12 @@ EOF
}
syscall_list() {
grep '^[0-9]' "$1" | sort -n | (
grep '^[0-9]' "$1" | sort -n |
while read nr abi name entry ; do
cat <<EOF
#if !defined(__NR_${name}) && !defined(__IGNORE_${name})
#warning syscall ${name} not implemented
#endif
EOF
echo "#if !defined(__NR_${name}) && !defined(__IGNORE_${name})"
echo "#warning syscall ${name} not implemented"
echo "#endif"
done
)
}
(ignore_list && syscall_list $(dirname $0)/../arch/x86/entry/syscalls/syscall_32.tbl) | \