Try to repro slow docker sync volume behavior

repro.sh

#!/bin/bash

mountdir=/mnt/testdir
touch f{1..10000}.txt

c1=$(docker run -d --rm -v "/$PWD:$mountdir" -w /$mountdir debian sleep 60)
c2=$(docker run -d --rm -v "/$PWD:$mountdir" -w /$mountdir debian sleep 60)

docker exec  -w /$mountdir $c1 bash -c "echo -n 'files found inside before removal: ' && echo f*.txt | wc -w"
docker stop -t0 $c1
rm f*.txt
docker run --rm -v "/$PWD:$mountdir" -w /$mountdir debian bash -c "echo -n 'files found inside after removal: ' && echo f*.txt | fgrep -v 'f*.txt' | wc -w"