I was quite surprised when running openssl speed today, and got 0.00s
as user time for everything. This is on a RH 6.2 box.
I found this *very* interesting little thing in
/usr/include/linux/time.h:
/* ISO/IEC 9899:1990 7.12.1: <time.h>
The macro `CLOCKS_PER_SEC' is the number per second of the value
returned by the `clock' function. */
/* CAE XSH, Issue 4, Version 2: <time.h>
The value of CLOCKS_PER_SEC is required to be 1 million on all
XSI-conformant systems. */
# define CLOCKS_PER_SEC 1000000
# ifndef __STRICT_ANSI__
/* Even though CLOCKS_PER_SEC has such a strange value CLK_TCK
presents the real value for clock ticks per second for the system. */
# define CLK_TCK 100
# endif
And in /usr/include/time.h, unless CLK_TCK is already defined, it will
be defined to the value of CLOCKS_PER_SEC.
Now, it seems like results might differ depending on if you compile a
program using this with -ansi or not. And actually, if I define HZ to
100.0 in all cases in apps/speed.c, I get a result that's at least
different from 0.00s (0.21s for 1024 bit private RSA's and 0.59s for
1024 bit public RSA's).
I'm quite dubious about this whole tick business. Any comments?
--
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