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Diffstat (limited to 'doc/crypto/OPENSSL_instrument_bus.pod')
-rw-r--r-- | doc/crypto/OPENSSL_instrument_bus.pod | 42 |
1 files changed, 0 insertions, 42 deletions
diff --git a/doc/crypto/OPENSSL_instrument_bus.pod b/doc/crypto/OPENSSL_instrument_bus.pod deleted file mode 100644 index 4ed83e4950b7..000000000000 --- a/doc/crypto/OPENSSL_instrument_bus.pod +++ /dev/null @@ -1,42 +0,0 @@ -=pod - -=head1 NAME - -OPENSSL_instrument_bus, OPENSSL_instrument_bus2 - instrument references to memory bus - -=head1 SYNOPSIS - - #ifdef OPENSSL_CPUID_OBJ - size_t OPENSSL_instrument_bus (int *vector,size_t num); - size_t OPENSSL_instrument_bus2(int *vector,size_t num,size_t max); - #endif - -=head1 DESCRIPTION - -It was empirically found that timings of references to primary memory -are subject to irregular, apparently non-deterministic variations. The -subroutines in question instrument these references for purposes of -gathering entropy for random number generator. In order to make it -bus-bound a 'flush cache line' instruction is used between probes. In -addition probes are added to B<vector> elements in atomic or -interlocked manner, which should contribute additional noise on -multi-processor systems. This also means that B<vector[num]> should be -zeroed upon invocation (if you want to retrieve actual probe values). - -OPENSSL_instrument_bus performs B<num> probes and records the number of -oscillator cycles every probe took. - -OPENSSL_instrument_bus2 on the other hand B<accumulates> consecutive -probes with the same value, i.e. in a way it records duration of -periods when probe values appeared deterministic. The subroutine -performs at most B<max> probes in attempt to fill the B<vector[num]>, -with B<max> value of 0 meaning "as many as it takes." - -=head1 RETURN VALUE - -Return value of 0 indicates that CPU is not capable of performing the -benchmark, either because oscillator counter or 'flush cache line' is -not available on current platform. For reference, on x86 'flush cache -line' was introduced with the SSE2 extensions. - -Otherwise number of recorded values is returned. |