On Mon, Mar 23, 2009 at 7:12 AM, Dan Nicholson <dbn.li...@gmail.com> wrote:
> On Fri, Mar 20, 2009 at 4:44 PM, Bruce Dubbs <bruce.du...@gmail.com> wrote:
>> Dan Nicholson wrote:
>>> On Fri, Mar 20, 2009 at 11:15 AM, Bruce Dubbs <bruce.du...@gmail.com> wrote:
>>>> Dan Nicholson wrote:
>>>>
>>>>> A while back I sanitized the bootscripts for POSIX sh compatibility, and
>>>>> I think DJ has been maintaining that goal. I think it's a nice (and
>>>>> obtainable) goal to target since having sh != bash can save on bloat.
>>>> Save on bloat? For what? My copy of bash is 500K. dash is about 80K.
>>>
>>> Right, bash is 4 times the size of dash. That adds up when you're forking
>>> the
>>> shell a hundred times or whatever during boot.
>>
>> Come on Dan. You know better than that. When you fork a program, the code
>> segment is not duplicated, but only any necessary data. For that, there
>> would
>> be no significant difference between bash and dash.
>
> I don't honestly know how much memory is duplicated or not. Here's a
> loop of shells that simply fork, do nothing and exit.
>
> $ time { for n in {0..100}; do /bin/bash -c :; done; }
>
> real 0m0.431s
> user 0m0.227s
> sys 0m0.191s
> $ time { for n in {0..100}; do /bin/dash -c :; done; }
>
> real 0m0.159s
> user 0m0.048s
> sys 0m0.120s
>
> Clearly, it is taking more time for the bash shell. I know you are
> going to say we're only talking about hundredths of seconds for each
> run, so why should we care. But it's more than double relatively.
>
> If you were looking at a system (not just a computer system) and you
> found that one part took twice the resources and twice as long to
> start up as another part offering similar functionality, why would you
> dismiss it? Maybe the original part offers better features than the
> replacement, but that doesn't mean the other facts can be ignored.
>
>>> The last time I tested, it shaved like 4 seconds off boot using dash instead
>>> of bash.
>>>
>>> http://linuxfromscratch.org/pipermail/lfs-support/2008-February/034192.html
>>
>>> I use bash all the time and I wouldn't consider using a minimal posix shell
>>> for my login shell. For any non-trivial script, I use bash. However, for a
>>> generic shell script, I don't know why you couldn't make it posix compliant.
>>> That allows people to have flexibility without much loss. The bootscripts
>>> are
>>> pretty simple.
>>
>> As you mention, bootscripts are pretty simple and in no way are a stress
>> test.
>> Four seconds doesn't seem very significant to me. It's not enough to notice
>> unless you are doing a timing test.
>
> 4 seconds out of 18 total is something I consider very significant.
> For you, maybe it's not, but you are free to keep /bin/bash as
> /bin/sh. However, you agree that the bootscripts are simple, so why do
> you need to use bash again?
>
> Let's just forget about it. I think this is the second or third time
> we've had this conversation and I think we just say the same things
> back and forth.
>
> --
> Dan
> --
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The last time we decided to make everything work w/ ash (sh), There
was not much benefit to utilizing bash specific features at the time.
--
Nathan Coulson (conathan)
------
Location: Brittish Columbia, Canada
Timezone: PST (-8)
Webpage: http://www.nathancoulson.com
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