On Fri, 2014-10-03 at 09:20 -0700, Russ Allbery wrote:
> Russell Stuart <russell-debian@stuart.id.au> writes:
> > I looks to me like you are re-writing history.
>
> I'm not sure how you meant this, but to note, this sentence made me very
> sad, since it felt like you believe I'm being intentionally dishonest with
> you. I'm really not, although I'm not sure how to convince you of that.
You convinced me I was wrong a few sentences later.
> I thought that's what you were getting at when talking about
> testing
Not really. I'm about documentation reflecting reality. Think of
putting an electrical component whose documentation says its 200 degrees
on a motherboard, only to find it fails at 190. When you ask why, is
"well we design it for 200, but only test it to 180" a satisfying
answer?
You have convinced me that in this case it's going to have to be that
way, so my prejudices notwithstanding. I've rationalised the pain away
by deciding it's no so bad as any competent programmer could see that is
it only tested to 190 regardless of what the standards say.
> Oh! I didn't realize or internalize that you were proposing switching the
> default shell to posh from dash. Yes, that would certainly improve our
> compliance with Policy considerably.
It's attractive because makes Policy more relevant - but only because of
that. Now that I think about it, switching pbuilder to posh would be
almost as good. Any additional pain would not be worth the effort.
If Debian was going to switch to another shell, I'd vote for the one in
busybox. That's because on desktop machines it doesn't matter, but on
embedded architectures it does - and they use busybox. So switching to
busybox would extend Debian's reach.
> If the speed is comparable
Here are two benchmarks. I did others. These demonstrate the extremes:
$ time dash -c 'i=0; while [ $i -lt 10000000 ]; do echo -n; i=$(($i + 1)); done'
real 0m16.695s
user 0m16.684s
sys 0m0.000s
$ time posh -c 'i=0; while [ $i -lt 10000000 ]; do echo -n; i=$(($i + 1)); done'
real 0m41.899s
user 0m41.872s
sys 0m0.000s
$ time busybox sh -c 'i=0; while [ $i -lt 10000000 ]; do echo -n; i=$(($i + 1)); done'
real 0m27.938s
user 0m25.160s
sys 0m2.760s
$ time bash -c 'i=0; while [ $i -lt 10000000 ]; do echo -n; i=$(($i + 1)); done'
real 1m7.971s
user 1m7.928s
sys 0m0.000s
$ time dash -c 'x="aaaaaaaaaaaaaaa"; t() { local x=$1; echo $x; }; while [ "${x%b}" = "${x}" ]; do y=; while :; do z="${x#b}"; [ "$z" != "$x" ] || break; y=a$y x=$z; done; x=$(t ${y}b${x#a}); done'
real 0m1.577s
user 0m0.204s
sys 0m0.500s
$ time posh -c 'x="aaaaaaaaaaaaaaa"; t() { local x=$1; echo $x; }; while [ "${x%b}" = "${x}" ]; do y=; while :; do z="${x#b}"; [ "$z" != "$x" ] || break; y=a$y x=$z; done; x=$(t ${y}b${x#a}); done'
real 0m2.232s
user 0m0.316s
sys 0m0.536s
$ time busybox sh -c 'x="aaaaaaaaaaaaaaa"; t() { local x=$1; echo $x; }; while [ "${x%b}" = "${x}" ]; do y=; while :; do z="${x#b}"; [ "$z" != "$x" ] || break; y=a$y x=$z; done; x=$(t ${y}b${x#a}); done'
real 0m2.104s
user 0m0.284s
sys 0m0.516s
$ time bash -c 'x="aaaaaaaaaaaaaaa"; t() { local x=$1; echo $x; }; while [ "${x%b}" = "${x}" ]; do y=; while :; do z="${x#b}"; [ "$z" != "$x" ] || break; y=a$y x=$z; done; x=$(t ${y}b${x#a}); done'
real 0m4.849s
user 0m0.892s
sys 0m0.740s
$
It looks like moving to dash sped Debian up a little.
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