Hi, I have a use case where I run grep with a large number of search patterns on a large text file. It works well with grep-3.3, but with grep-3.4 it quickly burned through GBs of memory and almost locked up my system due to swapping.
To avoid attaching those large files, I could mostly reproduce the effects like this: ulimit -d 5000000 # avoid system lockup due to excessive swapping export LC_ALL=C # make sure no Unicode case conversions are needed % time ./grep-3.3 -Fwif <(seq 300000 | tr 0-9 A-J) <<<foo real 0m0.054s user 0m0.048s sys 0m0.012s % time ./grep-3.4 -Fwif <(seq 30000 | tr 0-9 A-J) <<<foo ./grep-3.4: Memory exhausted Aborted real 0m1.291s user 0m0.696s sys 0m0.599s % time ./grep-3.6 -Fwif <(seq 300000 | tr 0-9 A-J) <<<foo real 0m13.162s user 0m12.955s sys 0m0.211s grep-3.3 behaves well, even with much larger number of patterns. Time seems to grow linearly, and memory usage is constant. grep-3.4 behaves the worst of these 3 versions. Even with just 30000 patterns it exceeds the ulimit of 5 GB. grep-3.6 behaves a bit better than 3.4, but still bad. Time seems to be quadratic in the number of patterns, and though memory usage in this case seems to be almost constant, in my actual use case it also runs out of memory where grep-3.3 works well with just a few 100 MB used. Without "-i", grep-3.4 seems to run as fast as grep-3.3, but grep-3.6 is almost as slow as with "-i". So there might actually be two different issues here, one that affects 3.4 with "-i" and one that affects 3.6 with or without "-i". Regards, Frank
