Re: Speed of rc

[John (Most modern computers would break if you stood on them) Mackin <john@ civil.su.oz.au>]

Summary: Dave Mason shows us, once again, that shots from the hip
usually miss.

    rc will have a significantly larger environment (rc functions) than
    sh, and many systems have *abysmal* exec performance because of the
    time spent copying the environment.

I don't know if you just didn't bother to read my mail, Dave, or what.
rc and sh were both being executed with precisely the same environment.
So whatever contribution exec makes in copying the environment will
have been the same for both.

For the record, I just did a wc of my environment and it is around 2100
characters.

As to `rc functions,' never forget than an important factor in the
_startup_ time of Byron's rc is that it imports functions lazily.
Of course, startup time is specifically not at issue here.

    So, John: try a version of rc with an empty environment.  I suspect
    the system times will be as fast as those for sh.

BZZZZZT!  Sorry, Player One, you lose this time, but thanks for trying...

: mod;; env - sh
$ /bin/time /bin/sh -c '/bin/cat pus2 | /usr/local/bin/rc'
       27.5 real         1.3 user        24.7 sys  
$ /bin/time /bin/sh -c '/bin/cat pus2 | /usr/local/bin/rc'
       27.7 real         1.2 user        25.1 sys  
$ /bin/time /bin/sh -c '/bin/cat pus2 | /usr/local/bin/rc'
       27.5 real         1.1 user        25.0 sys  
$ /bin/time /bin/sh -c '/bin/cat pus2 | /usr/local/bin/rc'
       27.4 real         1.1 user        24.7 sys  
$ /bin/time /bin/sh -c '/bin/cat pus2 | /bin/sh'
       17.2 real         1.3 user        14.9 sys  
$ /bin/time /bin/sh -c '/bin/cat pus2 | /bin/sh'
       16.8 real         1.4 user        14.4 sys  
$ /bin/time /bin/sh -c '/bin/cat pus2 | /bin/sh'
       16.8 real         1.5 user        14.2 sys  
$ /bin/time /bin/sh -c '/bin/cat pus2 | /bin/sh'
       16.9 real         1.4 user        14.8 sys  

Clearly, with an empty environment, we can't do any path searching,
so I tried only pus2 this time, with the "./xx"s in it.

We still see rc using a much higher system time than sh.  Interestingly,
sh's user-time has come down to on a par with rc's.  I won't offer
any speculation on that one.

OK,
John.