$ grep '^model name' /proc/cpuinfo | head -1
model name	: Intel(R) Core(TM) i5-3470 CPU @ 3.20GHz


<< test1 >>

for (( i = 0; i < 1000000; i++ )); do
  printf 'aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaab\n'
done > test1.txt
printf 'aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa\n' >> test1.txt

time env LANG=ja_JP.eucJP src/grep -v b test1.txt

=== before the patch ===

$ time env LANG=ja_JP.eucJP src/grep -v b test1.txt
aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa

real    0m2.038s
user    0m1.967s
sys     0m0.071s

=== after the patch ===

$ time env LANG=ja_JP.eucJP src/grep -v b test1.txt
aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa

real    0m0.595s
user    0m0.536s
sys     0m0.060s


<< test2 >>

for (( i = 0; i < 4000000; i++ )); do
  printf '\xc2\xa2\xc2\xa2\xc2\xa2\xc2\xa2\xc2\xa2\xc2\xa2\xc2\xa2\xc2\xa2\xc2\xa2\xc2\xa3\n'
done > test2.txt
printf '\xc2\xa2\xc2\xa2\xc2\xa2\xc2\xa2\xc2\xa2\xc2\xa2\xc2\xa2\xc2\xa2\xc2\xa2\xc2\xa2\n' >> test2.txt

CHR=`printf '\xc2\xa3'`
time env LANG=ja_JP.UTF-8 src/grep -v "$CHR" test2.txt

=== before the patch ===

$ time env LANG=ja_JP.UTF-8 src/grep -v "$CHR" test2.txt
￠￠￠￠￠￠￠￠￠￠

real    0m1.460s
user    0m1.407s
sys     0m0.054s

=== after the patch ===

$ time env LANG=ja_JP.UTF-8 src/grep -v "$CHR" test2.txt
￠￠￠￠￠￠￠￠￠￠

real    0m0.560s
user    0m0.513s
sys     0m0.047s