Counter-intuitively, using sparse checkout in Cygwin degrades "status"
times as status appears to "stat" non-existent files and directories.
To demonstrate, I created a repo with 100k random files in a
dir/dir/dir/file structure (on a linux box -- to do this in Cygwin
requires piping the result of "openssl rand" to "dos2unix" as the output
contains "\r") and cloned in a Cygwin shell:
git init test
cd test
git commit --allow-empty -m 'Empty first commit'
for i in {1..10}; do for j in {1..10000}; do file=$( openssl rand -hex
32 | sed 's,^\(.\)\(.\)\(.\),\1/\2/\3/,'); mkdir -p $( dirname $file );
echo $file > $file ; done & done; wait
git add .
git commit -m '100000 files'
git gc --prune=now --aggressive
I then timed and plotted "git status" as sparse checkout step-wisely
reduced the number of files in the working tree using the folllowing
command:
( ( git status >& /dev/null; time -p git status > /dev/null ) |& sed -n
'/real/{s/real/100000/p}'; git config core.sparseCheckout true; for i in
$( seq 90000 -10000 10000 ) 1; do git ls-files | head -n $i | sed
's,^,/,' > .git/info/sparse-checkout; git read-tree -u -m HEAD; git
status >& /dev/null; ( time -p git status > /dev/null ) |& sed -n
"/real/{s/real/$i/p}"; done; echo '*' > .git/info/sparse-checkout; git
read-tree -u -m HEAD; rm .git/info/sparse-checkout; git config --unset
core.sparseCheckout ) | gnuplot -p -e "set terminal dumb; set xrange[]
reverse; set style data dots; set nokey; plot '-' using 1:2"
Vertical bar is time in seconds, horizontal the number of files in the
working tree after the sparse checkout.
Linux results (v2.1.0):
0.45
.+-----+------+-----+------+------+------+------+-----+------+-----++
+ + + + + + + + + + +
| |
0.4 ++ ++
| |
0.35 ++ ++
| |
| |
0.3 ++ . ++
| |
| . |
0.25 ++ . . ++
| . . |
| |
0.2 ++ . . ++
| |
0.15 ++ . +.
| |
+ + + + + + + + + + +
0.1
++-----+------+-----+------+------+------+------+-----+------+-----++
100000 90000 80000 70000 60000 50000 40000 30000 20000 10000 0
Cygwin results (v2.1.1):
10
++-----+------+------+------+------+------+------+------+------+-----++
+ + + + + + + + + + +
| .
9 ++ ++
| . |
| |
8 ++ . ++
| |
| |
7 ++ . ++
| |
| |
| . . |
6 ++ ++
| |
| |
5 ++ . ++
. . . |
+ + . + + + + + + + +
4
++-----+------+------+------+------+------+------+------+------+-----++
100000 90000 80000 70000 60000 50000 40000 30000 20000 10000 0
Linux times do what I expect/want (they get better as the number of
working tree files decrease), but Cygwin does the opposite: the worst
times are in a working tree with only 1 (sparse) file, and it's double
where I started with no sparse checkout! I'd hoped sparse checkout
would improve the too-slow status times when all files are present...
Looking at strace with a working tree consisting of a single (sparse)
file suggests Cygwin is attempting to access the non-existent files and
directories whereas Linux does not appear to do so. In fact, if I do
nothing more than "mkdir -p $( git ls-files | cut -c1-5 | sort -u )"
when looking at a single (sparse) file, I can drop status times below
3s, a 3-fold improvement and something at least better than where I started!
Is there a way I can get improved status times using sparse checkout
with Cygwin?
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