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author | Kerin Millar <kfm@plushkava.net> | 2024-06-08 16:44:32 +0100 |
---|---|---|
committer | Kerin Millar <kfm@plushkava.net> | 2024-06-14 01:27:42 +0100 |
commit | 72b754bb11066b10ae14b8f017f93ad5c62e7467 (patch) | |
tree | 6a3567c8907d71a9c57a47052dad8fa5cd33aa63 | |
parent | Have _eend() assume 80 columns in the absence of a smart terminal (diff) | |
download | gentoo-functions-72b754bb11066b10ae14b8f017f93ad5c62e7467.tar.gz gentoo-functions-72b754bb11066b10ae14b8f017f93ad5c62e7467.tar.bz2 gentoo-functions-72b754bb11066b10ae14b8f017f93ad5c62e7467.zip |
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; [ $i -eq 15000 ] && exit; done'
The results were as follows.
BEFORE
real 0m43.762s
user 0m22.202s
sys 0m21.415s
AFTER
real 0m3.470s
user 0m2.535s
sys 0m0.736s
Signed-off-by: Kerin Millar <kfm@plushkava.net>
-rw-r--r-- | functions.sh | 81 |
1 files changed, 78 insertions, 3 deletions
diff --git a/functions.sh b/functions.sh index fcba801..52224a5 100644 --- a/functions.sh +++ b/functions.sh @@ -19,6 +19,7 @@ # EINFO_LOG : whether printing functions should call esyslog() # EINFO_QUIET : whether info message printing functions should be silenced # EINFO_VERBOSE : whether v-prefixed functions should do anything +# EPOCHREALTIME : potentially used by _update_time() to get the time # IFS : multiple message operands are joined by its first character # INSIDE_EMACS : whether to work around an emacs-specific bug in _eend() # NO_COLOR : whether colored output should be suppressed @@ -920,15 +921,36 @@ _select_by_mtime() { } # +# Considers the first parameter as a number of deciseconds and determines +# whether fewer have elapsed since the last occasion on which the function was +# called. +# +_should_throttle() +{ + _update_time || return + if [ "$(( 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 "${COLUMNS}" else @@ -943,6 +965,59 @@ _update_columns() } # +# Determines either the number of deciseconds elapsed since the unix epoch or +# the number of deciseconds that the operating system has been online, depending +# on the capabilities of the shell and/or platform. Upon success, the obtained +# value shall be assigned to genfun_time. Otherwise, the return value shall be +# greater than 0. +# +_update_time() +{ + genfun_last_time=0 + + # shellcheck disable=3028 + if [ "${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 # terminal is detected, the level shall be 1. If a smart terminal is detected, |