Re: [PATCH] replace timeconst bc script with an sh script
From: Kieran Bingham
Date: Thu Jun 20 2019 - 03:28:45 EST
Hi Ethan,
Thank you for the patch,
On 20/06/2019 07:22, Ethan Sommer wrote:
> removes the bc build dependency introduced when timeconst.pl was
> replaced by timeconst.bc
Does this introduction of bc cause you problems when building?
Documentation/process/changes.rst states that "You will need bc to build
kernels 3.10 and higher"
Is bc used elsewhere in the kernel?
If this is the only use of BC and it is no longer a dependency - the
process document should be updated.
Though I see uses at:
tools/testing/selftests/net/forwarding/lib.sh
There is a small issue with quotes highlighted below, and the only other
(really minor) comment is performance.
time (echo 1000 | bc -q ./kernel/time/timeconst.bc)
real 0m0.006s
user 0m0.006s
sys 0m0.000s
vs
time /tmp/timeconst.sh 1000
real 0m0.176s
user 0m0.141s
sys 0m0.050s
So that's 176 milliseconds vs 6. (on an i7 gen8 laptop) which probably
isn't going to affect things too much on the scale of building a kernel.
But I measured it so I thought it was worth posting the results.
--
Regards
Kieran
> Signed-off-by: Ethan Sommer <e5ten.arch@xxxxxxxxx>
> ---
> Kbuild | 4 +-
> kernel/time/timeconst.bc | 117 --------------------------------------
> kernel/time/timeconst.sh | 118 +++++++++++++++++++++++++++++++++++++++
> 3 files changed, 120 insertions(+), 119 deletions(-)
> delete mode 100644 kernel/time/timeconst.bc
> create mode 100755 kernel/time/timeconst.sh
>
> diff --git a/Kbuild b/Kbuild
> index 8637fd14135f..2b5f2957cf04 100644
> --- a/Kbuild
> +++ b/Kbuild
> @@ -20,9 +20,9 @@ timeconst-file := include/generated/timeconst.h
>
> targets += $(timeconst-file)
>
> -filechk_gentimeconst = echo $(CONFIG_HZ) | bc -q $<
> +filechk_gentimeconst = $(CONFIG_SHELL) $< $(CONFIG_HZ)
>
> -$(timeconst-file): kernel/time/timeconst.bc FORCE
> +$(timeconst-file): kernel/time/timeconst.sh FORCE
> $(call filechk,gentimeconst)
>
> #####
> diff --git a/kernel/time/timeconst.bc b/kernel/time/timeconst.bc
> deleted file mode 100644
> index 7ed0e0fb5831..000000000000
> --- a/kernel/time/timeconst.bc
> +++ /dev/null
> @@ -1,117 +0,0 @@
> -/* SPDX-License-Identifier: GPL-2.0 */
> -
> -scale=0
> -
> -define gcd(a,b) {
> - auto t;
> - while (b) {
> - t = b;
> - b = a % b;
> - a = t;
> - }
> - return a;
> -}
> -
> -/* Division by reciprocal multiplication. */
> -define fmul(b,n,d) {
> - return (2^b*n+d-1)/d;
> -}
> -
> -/* Adjustment factor when a ceiling value is used. Use as:
> - (imul * n) + (fmulxx * n + fadjxx) >> xx) */
> -define fadj(b,n,d) {
> - auto v;
> - d = d/gcd(n,d);
> - v = 2^b*(d-1)/d;
> - return v;
> -}
> -
> -/* Compute the appropriate mul/adj values as well as a shift count,
> - which brings the mul value into the range 2^b-1 <= x < 2^b. Such
> - a shift value will be correct in the signed integer range and off
> - by at most one in the upper half of the unsigned range. */
> -define fmuls(b,n,d) {
> - auto s, m;
> - for (s = 0; 1; s++) {
> - m = fmul(s,n,d);
> - if (m >= 2^(b-1))
> - return s;
> - }
> - return 0;
> -}
> -
> -define timeconst(hz) {
> - print "/* Automatically generated by kernel/time/timeconst.bc */\n"
> - print "/* Time conversion constants for HZ == ", hz, " */\n"
> - print "\n"
> -
> - print "#ifndef KERNEL_TIMECONST_H\n"
> - print "#define KERNEL_TIMECONST_H\n\n"
> -
> - print "#include <linux/param.h>\n"
> - print "#include <linux/types.h>\n\n"
> -
> - print "#if HZ != ", hz, "\n"
> - print "#error \qinclude/generated/timeconst.h has the wrong HZ value!\q\n"
> - print "#endif\n\n"
> -
> - if (hz < 2) {
> - print "#error Totally bogus HZ value!\n"
> - } else {
> - s=fmuls(32,1000,hz)
> - obase=16
> - print "#define HZ_TO_MSEC_MUL32\tU64_C(0x", fmul(s,1000,hz), ")\n"
> - print "#define HZ_TO_MSEC_ADJ32\tU64_C(0x", fadj(s,1000,hz), ")\n"
> - obase=10
> - print "#define HZ_TO_MSEC_SHR32\t", s, "\n"
> -
> - s=fmuls(32,hz,1000)
> - obase=16
> - print "#define MSEC_TO_HZ_MUL32\tU64_C(0x", fmul(s,hz,1000), ")\n"
> - print "#define MSEC_TO_HZ_ADJ32\tU64_C(0x", fadj(s,hz,1000), ")\n"
> - obase=10
> - print "#define MSEC_TO_HZ_SHR32\t", s, "\n"
> -
> - obase=10
> - cd=gcd(hz,1000)
> - print "#define HZ_TO_MSEC_NUM\t\t", 1000/cd, "\n"
> - print "#define HZ_TO_MSEC_DEN\t\t", hz/cd, "\n"
> - print "#define MSEC_TO_HZ_NUM\t\t", hz/cd, "\n"
> - print "#define MSEC_TO_HZ_DEN\t\t", 1000/cd, "\n"
> - print "\n"
> -
> - s=fmuls(32,1000000,hz)
> - obase=16
> - print "#define HZ_TO_USEC_MUL32\tU64_C(0x", fmul(s,1000000,hz), ")\n"
> - print "#define HZ_TO_USEC_ADJ32\tU64_C(0x", fadj(s,1000000,hz), ")\n"
> - obase=10
> - print "#define HZ_TO_USEC_SHR32\t", s, "\n"
> -
> - s=fmuls(32,hz,1000000)
> - obase=16
> - print "#define USEC_TO_HZ_MUL32\tU64_C(0x", fmul(s,hz,1000000), ")\n"
> - print "#define USEC_TO_HZ_ADJ32\tU64_C(0x", fadj(s,hz,1000000), ")\n"
> - obase=10
> - print "#define USEC_TO_HZ_SHR32\t", s, "\n"
> -
> - obase=10
> - cd=gcd(hz,1000000)
> - print "#define HZ_TO_USEC_NUM\t\t", 1000000/cd, "\n"
> - print "#define HZ_TO_USEC_DEN\t\t", hz/cd, "\n"
> - print "#define USEC_TO_HZ_NUM\t\t", hz/cd, "\n"
> - print "#define USEC_TO_HZ_DEN\t\t", 1000000/cd, "\n"
> -
> - cd=gcd(hz,1000000000)
> - print "#define HZ_TO_NSEC_NUM\t\t", 1000000000/cd, "\n"
> - print "#define HZ_TO_NSEC_DEN\t\t", hz/cd, "\n"
> - print "#define NSEC_TO_HZ_NUM\t\t", hz/cd, "\n"
> - print "#define NSEC_TO_HZ_DEN\t\t", 1000000000/cd, "\n"
> - print "\n"
> -
> - print "#endif /* KERNEL_TIMECONST_H */\n"
> - }
> - halt
> -}
> -
> -hz = read();
> -timeconst(hz)
> diff --git a/kernel/time/timeconst.sh b/kernel/time/timeconst.sh
> new file mode 100755
> index 000000000000..df821988acbf
> --- /dev/null
> +++ b/kernel/time/timeconst.sh
> @@ -0,0 +1,118 @@
> +#!/bin/sh
> +# SPDX-License-Identifier: GPL-2.0
> +
> +if [ -z "$1" ]; then
> + printf '%s <HZ>\n' "$0"
> + exit 1
> +else
> + hz="$1"
> +fi
> +
> +# 2 to the power of n
> +pot() {
> + local i=1
> + local j=1
> + while [ "${j}" -le "$1" ]; do
> + i="$((i * 2))"
> + j="$((j + 1))"
> + done
> + printf '%s\n' "${i}"
> +}
> +
> +# Greatest common denominator
> +gcd() {
> + local i="$1"
> + local j="$2"
> + local k
> + while [ "${j}" -ne 0 ]; do
> + k="${j}"
> + j="$((i % j))"
> + i="${k}"
> + done
> + printf '%s\n' "${i}"
> +}
> +
> +# Division by reciprocal multiplication.
> +fmul() {
> + printf '%s\n' "$((($(pot "$1") * $2 + $3 - 1) / $3))"
> +}
> +
> +# Adjustment factor when a ceiling value is used.
> +fadj() {
> + local i="$(gcd "$2" "$3")"
> + printf '%s\n' "$(($(pot "$1") * ($3 / i - 1) / ($3 / i)))"
> +}
> +
> +# Compute the appropriate mul/adj values as well as a shift count,
> +# which brings the mul value into the range 2^b-1 <= x < 2^b. Such
> +# a shift value will be correct in the signed integer range and off
> +# by at most one in the upper half of the unsigned range.
> +fmuls() {
> + local i=0
> + local j
> + while true; do
> + j="$(fmul "${i}" "$2" "$3")"
> + if [ "${j}" -ge "$(pot "$(($1 - 1))")" ]; then
> + printf '%s\n' "${i}" && return
> + fi
> + i="$((i + 1))"
> + done
> +}
> +
> +printf '/* Automatically generated by %s */\n' "$0"
> +printf '/* Time conversion constants for HZ == %s */\n\n' "$1"
> +
> +printf '#ifndef KERNEL_TIMECONST_H\n'
> +printf '#define KERNEL_TIMECONST_H\n\n'
> +
> +printf '#include <linux/param.h>\n'
> +printf '#include <linux/types.h>\n\n'
> +
> +printf '#if HZ != %s\n' "$1"
> +printf '#error \qinclude/generated/timeconst.h has the wrong HZ value!\q\n'
This generates an incorrect output:
diff /tmp/bc.timed /tmp/sh.timed
1c1
< /* Automatically generated by kernel/time/timeconst.bc */
---
> /* Automatically generated by /tmp/timeconst.sh */
11c11
< #error "include/generated/timeconst.h has the wrong HZ value!"
---
> #error \qinclude/generated/timeconst.h has the wrong HZ value!\q
here ^ and here ^
> +printf '#endif\n\n'
> +
> +if [ "$1" -lt 2 ]; then
> + printf '#error Totally bogus HZ value!\n'
> + exit 1
> +fi
> +
> +s="$(fmuls 32 1000 "$1")"
> +printf '#define HZ_TO_MSEC_MUL32\tU64_C(0x%X)\n' "$(fmul "${s}" 1000 "$1")"
> +printf '#define HZ_TO_MSEC_ADJ32\tU64_C(0x%X)\n' "$(fadj "${s}" 1000 "$1")"
> +printf '#define HZ_TO_MSEC_SHR32\t%s\n' "${s}"
> +
> +s="$(fmuls 32 "$1" 1000)"
> +printf '#define MSEC_TO_HZ_MUL32\tU64_C(0x%X)\n' "$(fmul "${s}" "$1" 1000)"
> +printf '#define MSEC_TO_HZ_ADJ32\tU64_C(0x%X)\n' "$(fadj "${s}" "$1" 1000)"
> +printf '#define MSEC_TO_HZ_SHR32\t%s\n' "${s}"
> +
> +cd="$(gcd "$1" 1000)"
> +printf '#define HZ_TO_MSEC_NUM\t\t%s\n' "$((1000 / cd))"
> +printf '#define HZ_TO_MSEC_DEN\t\t%s\n' "$((hz / cd))"
> +printf '#define MSEC_TO_HZ_NUM\t\t%s\n' "$((hz / cd))"
> +printf '#define MSEC_TO_HZ_DEN\t\t%s\n\n' "$((1000 / cd))"
> +
> +s="$(fmuls 32 1000000 "$1")"
> +printf '#define HZ_TO_USEC_MUL32\tU64_C(0x%X)\n' "$(fmul "${s}" 1000000 "$1")"
> +printf '#define HZ_TO_USEC_ADJ32\tU64_C(0x%X)\n' "$(fadj "${s}" 1000000 "$1")"
> +printf '#define HZ_TO_USEC_SHR32\t%s\n' "${s}"
> +
> +s="$(fmuls 32 "$1" 1000000)"
> +printf '#define USEC_TO_HZ_MUL32\tU64_C(0x%X)\n' "$(fmul "${s}" "$1" 1000000)"
> +printf '#define USEC_TO_HZ_ADJ32\tU64_C(0x%X)\n' "$(fadj "${s}" "$1" 1000000)"
> +printf '#define USEC_TO_HZ_SHR32\t%s\n' "${s}"
> +
> +cd="$(gcd "$1" 1000000)"
> +printf '#define HZ_TO_USEC_NUM\t\t%s\n' "$((1000000 / cd))"
> +printf '#define HZ_TO_USEC_DEN\t\t%s\n' "$((hz / cd))"
> +printf '#define USEC_TO_HZ_NUM\t\t%s\n' "$((hz / cd))"
> +printf '#define USEC_TO_HZ_DEN\t\t%s\n' "$((1000000 / cd))"
> +
> +cd="$(gcd "$1" 1000000000)"
> +printf '#define HZ_TO_NSEC_NUM\t\t%s\n' "$((1000000000 / cd))"
> +printf '#define HZ_TO_NSEC_DEN\t\t%s\n' "$((hz / cd))"
> +printf '#define NSEC_TO_HZ_NUM\t\t%s\n' "$((hz / cd))"
> +printf '#define NSEC_TO_HZ_DEN\t\t%s\n' "$((1000000000 / cd))"
> +
> +printf '\n#endif /* KERNEL_TIMECONST_H */\n'
>
--
Regards
--
Kieran