Having bash-completion installed significantly slows down starting a new Cygwin Bash login shell. It's a problem I've noticed, and I've seen other users report it on this list and elsewhere, too. I've done a bit of digging into what the problem is, and what can be done about it-suggestions are at the bottom of this email.
The slow-down from using bash-completion is due to loading the contents of the
/etc/bash_completion.d/ directory. By adding `time` statements at various
ponits in /etc/bash_completion, I can see it's adding a fairly consistent 6-6.5
seconds to the shell startup time for me, which more-or-less matches my
subjective experience (starting Bash without bash-completion installed is
near-instant).
Drilling down, there are 187 different scripts in my /etc/bash_completion.d
(which, until today, should have been untouched by anything other than Cygwin
setup.exe). Average load times for me vary from less than a millisecond to
over 600 milliseconds. I've attached my analysis as a CSV; times are as
reported by Bash's `time` builtin for the time for /etc/bash_completion to dot
in that script.
A lot of the scripts are for things I don't have installed. The top four
scripts in terms of time taken (mailman, shadow, dsniff, e2fsprogs) do nothing
on my system, but between them alone add 1.5 seconds to the average Bash load
time. The top 4 seconds includes only two scripts I'm interested in (git and
gdb).
On my PC, I've renamed the majority of the scripts in /etc/bash_completion.d to
have a .bak extension, which prevents bash-completion from loading them. I've
kept 37 hand-selected scripts which I either do use or could forsee me using.
I'm now seeing Bash take less than a second to load, with picking up all the
scripts taking about 0.3 seconds.
To avoid others suffering in the same way, I can think of a few different
options, none of which are ideal:
- Add something to the Cygwin FAQ detailing a solution similar to the above.
Requires users to actively look for a solution, but requires minimal
effort. If people think this would be useful, I'm happy to draft something
up.
- Customize Cygwin's bash-completion package, removing scripts for functions
that don't exist in Cygwin. This is obviously additional work for the
package maintainer (although I'd be glad to help). This won't help for
packages that could be installed but aren't, however, but it's at least a
step.
- Split out the bash-completion script into separate packages that users can
install as needed. I suspect this is far more effort than it's worth,
however, both for users and maintainers.
- Something else yet to be suggested.
Regards,
Adam
--
Adam Dinwoodie
Messages posted to this list are made in a personal capacity.
times.csv
Description: times.csv
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