Re: [PATCH] bash completion: Improve responsiveness of git-log completion
On Sun, Jul 13, 2008 at 02:37:42AM +0000, Shawn O. Pearce wrote:
Show 20 quoted lines
> Junio noticed the bash completion has been taking a long time lately.
> Petr Baudis tracked it down to 72e5e989b ("bash: Add space after
> unique command name is completed."). Tracing the code showed
> we spent significant time inside of this loop within __gitcomp,
> due to the string copying overhead.
>
> [28.146109654] _git common over
> [28.164791148] gitrefs in
> [28.280302268] gitrefs dir out
> [28.300939737] gitcomp in
> [28.308378112] gitcomp pre-case
> * [28.313407453] gitcomp iter in
> * [28.701270296] gitcomp iter out
> [28.713370786] out normal
>
> Since __git_refs avoids this string copying by forking and using
> echo we use the same trick here when we need to finish generating
> the names for the caller.
>
> Signed-off-by: Shawn O. Pearce <spearce@spearce.org>I spent quite some time trying to optimize the run by heavy use of bash arrays (either just in __gitcomp() and at later stage reusing __git_refs() array within __gitcomp()), but it turned out I have made few simple mistakes and in the end, the array is slower than Shawn's approach - when reusing the array, the difference is even bigger. I think that if a[i]=x is slower than echo x, bash is doing something real weird, but that seems to be the case.
Someone might find my simple and noisy benchmarker useful:
Show changes to contrib/completion/git-completion.bash +38 −2
diff --git a/contrib/completion/git-completion.bash b/contrib/completion/git-completion.bash
index 27332ed..31f97c1 100755
--- a/contrib/completion/git-completion.bash
+++ b/contrib/completion/git-completion.bash
@@ -45,6 +45,18 @@
# git@vger.kernel.org
#
+
+benchmark_last=0
+benchmark_delta=0
+benchmark ()
+{
+ #return
+ local now=$(date +%S%N)
+ benchmark_diff=$(echo "($now-$benchmark_last)/1000000-($benchmark_delta)"|bc)
+ echo "[+${benchmark_diff}ms] $*" >&2
+ benchmark_last=$now
+}
+
__gitdir ()
{
if [ -z "$1" ]; then
@@ -116,6 +128,7 @@ __git_ps1 ()
__gitcomp ()
{
+ benchmark "gitcomp start"
local all c s=$'\n' IFS=' '$'\t'$'\n'
local cur="${COMP_WORDS[COMP_CWORD]}"
if [ $# -gt 2 ]; then
@@ -138,6 +151,7 @@ __gitcomp ()
esac
IFS=$s
COMPREPLY=($(compgen -P "$2" -W "$all" -- "$cur"))
+ benchmark "gitcomp end"
return
}
@@ -185,12 +199,16 @@ __git_tags ()
__git_refs ()
{
+ benchmark "gitrefs in"
local cmd i is_hash=y dir="$(__gitdir "$1")"
if [ -d "$dir" ]; then
if [ -e "$dir/HEAD" ]; then echo HEAD; fi
- for i in $(git --git-dir="$dir" \
+ benchmark "gitrefs dir a"
+ local a=($(git --git-dir="$dir" \
for-each-ref --format='%(refname)' \
- refs/tags refs/heads refs/remotes); do
+ refs/tags refs/heads refs/remotes))
+ benchmark "gitrefs dir r"
+ for i in "${a[@]}"; do
case "$i" in
refs/tags/*) echo "${i#refs/tags/}" ;;
refs/heads/*) echo "${i#refs/heads/}" ;;
@@ -198,6 +216,7 @@ __git_refs ()
*) echo "$i" ;;
esac
done
+ benchmark "gitrefs dir out"
return
fi
for i in $(git ls-remote "$dir" 2>/dev/null); do
@@ -210,6 +229,7 @@ __git_refs ()
n,*) is_hash=y; echo "$i" ;;
esac
done
+ benchmark "gitrefs out"
}
__git_refs2 ()
@@ -324,7 +344,9 @@ __git_complete_revlist ()
__gitcomp "$cur."
;;
*)
+ benchmark "revlist simple in"
__gitcomp "$(__git_refs)"
+ benchmark "revlist simple out"
;;
esac
}
@@ -756,6 +778,8 @@ _git_log ()
{
__git_has_doubledash && return
+ benchmark "doubledash over"
+
local cur="${COMP_WORDS[COMP_CWORD]}"
case "$cur" in
--pretty=*)
@@ -791,6 +815,7 @@ _git_log ()
return
;;
esac
+ benchmark "gitcomp over"
__git_complete_revlist
}
@@ -1303,6 +1328,9 @@ _git ()
{
local i c=1 command __git_dir
+ benchmark "in"; benchmark_delta=0
+ benchmark "in netto"; benchmark_delta=$benchmark_diff
+
while [ $c -lt $COMP_CWORD ]; do
i="${COMP_WORDS[c]}"
case "$i" in
@@ -1314,6 +1342,8 @@ _git ()
c=$((++c))
done
+ #[ "$__git_dir" ] || __git_dir="$(__gitdir)"
+
if [ -z "$command" ]; then
case "${COMP_WORDS[COMP_CWORD]}" in
--*=*) COMPREPLY=() ;;
@@ -1330,12 +1360,16 @@ _git ()
;;
*) __gitcomp "$(__git_commands) $(__git_aliases)" ;;
esac
+
+ benchmark "out cut $(date +%S.%N)"
return
fi
local expansion=$(__git_aliased_command "$command")
[ "$expansion" ] && command="$expansion"
+ benchmark "mark common"
+
case "$command" in
am) _git_am ;;
add) _git_add ;;
@@ -1374,6 +1408,8 @@ _git ()
whatchanged) _git_log ;;
*) COMPREPLY=() ;;
esac
+
+ benchmark "out normal"
}
_gitk ()
Shawn O. Pearce
