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Re: for; do; done regression ?


From: Chet Ramey
Subject: Re: for; do; done regression ?
Date: Fri, 07 Jan 2011 10:39:58 -0500
User-agent: Mozilla/5.0 (Macintosh; U; Intel Mac OS X 10.5; en-US; rv:1.9.2.13) Gecko/20101207 Thunderbird/3.1.7

On 1/7/11 10:03 AM, Chet Ramey wrote:
> On 1/6/11 8:17 PM, Alexander Tiurin wrote:
>> Hi!
>>
>> I ran the command 
>>
>> ~$ time for i in `seq 0 10000`  ; do echo /o/23/4 | cut -d'/' -f2 ; done
>>> /dev/null 
>>
>> 6 times in a row, and noticed to the increase in execution time:
>>
>       [...]
>>
>> how to interpret the results?
> 
> It's hard to say without doing more investigation, but I suspect that the
> fork time is increasing because the bash binary is growing in size.
> 
> I'd have to build a version with profiling enabled to tell for sure.

I built a profiling version of bash-4.2 (without the bash malloc, since
linux doesn't let you replace malloc when you're profiling), and the
execution time was dominated by fork: around 55-60% of the time.  That's
around 10-15 times more than any other function.

Chet
-- 
``The lyf so short, the craft so long to lerne.'' - Chaucer
                 ``Ars longa, vita brevis'' - Hippocrates
Chet Ramey, ITS, CWRU    address@hidden    http://cnswww.cns.cwru.edu/~chet/



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