commit: 72b754bb11066b10ae14b8f017f93ad5c62e7467
Author: Kerin Millar <kfm <AT> plushkava <DOT> net>
AuthorDate: Sat Jun 8 15:44:32 2024 +0000
Commit: Sam James <sam <AT> gentoo <DOT> org>
CommitDate: Fri Jun 14 00:27:42 2024 +0000
URL:
https://gitweb.gentoo.org/proj/gentoo-functions.git/commit/?id=72b754bb
Throttle the rate at which genfun_cols may be refreshed
Limit the rate at which genfun_cols can be refreshed to intervals that
are no shorter than 5 decisconds (half a second). Doing so renders
repeated calls to the _eend() function at short intervals faster by an
order of magnitude.
On one of my fastest available machines, I performed the following
benchmark with bash 5.2.26.
$ time for ((i=0; i<50000; i++)); do ebegin "$i"; eend; done
The results were as follows.
BEFORE
real 0m56.897s
user 0m16.990s
sys 0m28.540s
AFTER
real 0m6.663s
user 0m6.435s
sys 0m0.191s
On one of my slowest available machines, I performed the following
benchmark with bash 5.2.26.
$ time for ((i=0; i<15000; i++)); do ebegin "$i"; eend; done
The results were as follows.
BEFORE
real 0m52.557s
user 0m34.484s
sys 0m18.231s
AFTER
real 0m11.422s
user 0m10.654s
sys 0m0.535s
On that same (slow) machine, I performed the following benchmark with
dash 0.5.12.
$ time dash -c '
. ./functions.sh
while :; do ebegin $((i+=1)); eend; [ $i -eq 15000 ] && exit; done'
The results were as follows.
BEFORE
real 0m43.762s
user 0m22.202s
sys 0m21.415s
AFTER
real 0m3.470s
user 0m2.535s
sys 0m0.736s
Signed-off-by: Kerin Millar <kfm <AT> plushkava.net>
functions.sh | 81 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++---
1 file changed, 78 insertions(+), 3 deletions(-)
diff --git a/functions.sh b/functions.sh
index fcba801..52224a5 100644
--- a/functions.sh
+++ b/functions.sh
@@ -19,6 +19,7 @@
# EINFO_LOG : whether printing functions should call esyslog()
# EINFO_QUIET : whether info message printing functions should be silenced
# EINFO_VERBOSE : whether v-prefixed functions should do anything
+# EPOCHREALTIME : potentially used by _update_time() to get the time
# IFS : multiple message operands are joined by its first character
# INSIDE_EMACS : whether to work around an emacs-specific bug in _eend()
# NO_COLOR : whether colored output should be suppressed
@@ -919,16 +920,37 @@ _select_by_mtime() {
| { IFS= read -r line && printf '%s\n' "${line#* }"; }
}
+#
+# Considers the first parameter as a number of deciseconds and determines
+# whether fewer have elapsed since the last occasion on which the function was
+# called.
+#
+_should_throttle()
+{
+ _update_time || return
+ if [ "$(( genfun_time - genfun_last_time > $1 ))" -eq 1 ]; then
+ genfun_last_time=${genfun_time}
+ false
+ fi
+}
+
#
# Determines whether the terminal on STDIN is able to report its dimensions.
# Upon success, the number of columns shall be stored in genfun_cols.
#
_update_columns()
{
- # Command substitutions are rather slow in bash. Using the COLUMNS
- # variable helps but checkwinsize won't work properly in subshells.
+ # Two optimisations are applied. Firstly, the rate at which updates can
+ # be performed is throttled to intervals of 5 deciseconds. Secondly, if
+ # running on bash then the COLUMNS variable may be gauged, albeit only
+ # in situations where doing so can be expected to work reliably; not if
+ # in a subshell. Note that executing true(1) is faster than executing
+ # stty(1) within a comsub.
# shellcheck disable=3028,3044
- if [ "$$" = "${BASHPID}" ] && shopt -q checkwinsize; then
+ if _should_throttle 5; then
+ test "${genfun_cols}"
+ return
+ elif [ "$$" = "${BASHPID}" ] && shopt -q checkwinsize; then
"${genfun_bin_true}"
set -- 0 "${COLUMNS}"
else
@@ -942,6 +964,59 @@ _update_columns()
[ "$#" -eq 2 ] && is_int "$2" && [ "$2" -gt 0 ] && genfun_cols=$2
}
+#
+# Determines either the number of deciseconds elapsed since the unix epoch or
+# the number of deciseconds that the operating system has been online,
depending
+# on the capabilities of the shell and/or platform. Upon success, the obtained
+# value shall be assigned to genfun_time. Otherwise, the return value shall be
+# greater than 0.
+#
+_update_time()
+{
+ genfun_last_time=0
+
+ # shellcheck disable=3028
+ if [ "${BASH_VERSINFO:-0}" -ge 5 ]; then
+ # shellcheck disable=2034,3045
+ _update_time()
+ {
+ local ds s timeval
+
+ timeval=${EPOCHREALTIME}
+ s=${timeval%.*}
+ printf -v ds '%.1f' ".${timeval#*.}"
+ if [ "${ds}" = "1.0" ]; then
+ ds=10
+ else
+ ds=${ds#0.}
+ fi
+ genfun_time=$(( s * 10 + ds ))
+ }
+ elif [ -f /proc/uptime ]; then
+ _update_time()
+ {
+ local ds s timeval
+
+ IFS=' ' read -r timeval _ < /proc/uptime || return
+ s=${timeval%.*}
+ printf -v ds '%.1f' ".${timeval#*.}"
+ if [ "${ds}" = "1.0" ]; then
+ ds=10
+ else
+ ds=${ds#0.}
+ fi
+ genfun_time=$(( s * 10 + ds ))
+ }
+ else
+ _update_time()
+ {
+ false
+ }
+ fi
+
+ _update_time
+}
+
#
# Grades the capability of the terminal attached to STDIN, assigning the level
# to genfun_tty. If no terminal is detected, the level shall be 0. If a dumb
