Package: diff Version: 1:3.0-1 Severity: normal Dear Maintainer,
ever since installing stretch, I have the feeling that diff became slower. Today, I had to compare two large text files (~1.3GB) with many small changes - essentially the output of a recursive md5sum. Some phone calls and two hours later, I interrupted diff and tried to do the same with diff --speed-large-files, as the files (very likely) are large files with sprinkled changes, as only a few lines (file md5s) are expected to have changed. This didn't seem to have an effect. Since I do this kind of diff rarely but consistently, and I thought diff should be faster than that, I randomly downloaded diffutils-2.9 from ftp.gnu.org and compiled it with some minor portability fixes. Indeed, diff from diffutils-2.9 managed to give me the diff in 132s, whether I specify --speed-large-files or not, which is an acceptable time. I tried to run debians diff with LC_ALL=C, to see if that might cause a problem (as grep had similar regressions), but gave up after about 20 minutes of runtime. So sometime between diffutils-2.9 and debian stretch's version there has been at least a 54 times slowdown for diff, to the point where diff becomes useless for large files. Note that 54 slowdown is only a lower bound, as I didn't have the patience to wait for more than two hours. Not sure if regressions of this type are considered a bug or simply a wishlist, but diff does use it's usefulness if it fails to provide output within hours where it used to only need minutes. -- System Information: Debian Release: 9.1 APT prefers stable APT policy: (990, 'stable'), (500, 'stable-updates'), (500, 'unstable'), (500, 'testing'), (1, 'experimental') Architecture: amd64 (x86_64) Foreign Architectures: i386 Kernel: Linux 4.9.61-040961-generic (SMP w/8 CPU cores) Locale: LANG=C, LC_CTYPE=en_US.UTF-8 (charmap=UTF-8), LANGUAGE=C (charmap=UTF-8) Shell: /bin/sh linked to /usr/bin/bash Init: systemd (via /run/systemd/system) Versions of packages diff depends on: ii diffutils 1:3.5-3 diff recommends no packages. diff suggests no packages. -- no debconf information
