Hi misi,

> you almost convinced me with the disk time...
>
> but that is not true. Reading the same file with a command like grep,
> takes 567msecs.
> try
>
> time grep XXXXXXXXXXX ./all3.c #this will not find anything, but will
> process all the file.. and no mmap is used!!!!!
> the result is:

The problem with "the time it takes to read" in Unix is elusive.
It depends on the number of real physical reads Unix has to do.
If the data is already in the buffers, the performance is much better.
Example (with a 27MB file I had not been using in advance):

(aca) root /e/ita > time grep zxdfgghjjkk voci.txt

real 0m1.342s
user 0m0.028s
sys 0m0.048s
(aca) root /e/ita > time grep zxdfgghjjkk voci.txt

real 0m0.093s
user 0m0.040s
sys 0m0.024s
(aca) root /e/ita > time grep zxdfgghjjkk voci.txt

real 0m0.088s
user 0m0.028s
sys 0m0.036s
(aca) root /e/ita > time grep zxdfgghjjkk voci.txt

real 0m0.082s
user 0m0.032s
sys 0m0.028s
(aca) root /e/ita > time grep zxdfgghjjkk voci.txt

real 0m0.062s
user 0m0.016s
sys 0m0.028s
(aca) root /e/ita > time grep zxdfgghjjkk voci.txt

real 0m0.055s
user 0m0.024s
sys 0m0.020s
(aca) root /e/ita > time grep zxdfgghjjkk voci.txt

real 0m0.077s
user 0m0.024s
sys 0m0.036s
(aca) root /e/ita > time grep zxdfgghjjkk voci.txt

real 0m0.049s
user 0m0.020s
sys 0m0.024s
(aca) root /e/ita > ll voci.txt
-rwxrwxr-x 1 root users 27338279 15 mag 2007 voci.txt

I don't know in which conditions you performed your tests,
but ideally you should reboot once per each test, and
perform the test without having used the file in advance,
in order to be sure that the Unix buffers are empty (of
the tested file).

Then a comparison can be safely used.

Cheers, Antonio
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