Commit d21832e2 authored Jun 01, 2017 by Arnd Bergmann Committed by Masahiro Yamada Jun 10, 2017

kbuild: speed up checksyscalls.sh



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>

parent 6f0fa58e

scripts/checksyscalls.sh

+4 −7

Original line number	Diff line number	Diff line
		@@ -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) \| \

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