Parallelizing bootscripts [was: Make bootscripts more POSIX compliant]

Bruce Dubbs bruce.dubbs at gmail.com
Tue Feb 20 13:28:49 PST 2007


Dan Nicholson wrote:
> On 2/20/07, TheOldFellow <theoldfellow at gmail.com> wrote:
>> Dan's OP was 'use dash to speed up booting' (over-compressed
>> over-simplification).  I said you'd do better by parallelising the
>> service start ups.  Nothing here that says it's at all worth while to do
>> either really.  It's an intellectual exercise!
> 
> I never said that it was going to make a significant difference, but
> it that if you're going to spawn a bunch of shell scripts, it would
> make sense to use the interpreter that's 1/6 the size of the other.
> 
> $ time { for (( i = 0; i < 20; i++ )); do /bin/bash -c ":"; done; }
> 
> real    0m0.034s
> user    0m0.014s
> sys     0m0.020s
> $ time { for (( i = 0; i < 20; i++ )); do /bin/dash -c ":"; done; }
> 
> real    0m0.015s
> user    0m0.004s
> sys     0m0.011s

OK, let's analyze this.  20 invocations.  19 ms difference.  Less than 1
ms wall clock time per invocation.  How much time did you want to put in
on this?  :)

The memory space is generally not significant either because only one
copy of the code is in memory at any time.  The difference would be data
space.

What *would* be useful, IMO, is to have a copy of the messages that the
bootscripts or subordinate programs write, including errors, sent to a
boot log.

  -- Bruce



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