I understand that this function deals with big numbers and this could
possibly explain the extra CPU usage on a 32 bit system. Is moving to
a 64 bit system the only option?

Regards,
Sudarshan

On Mon, Jun 4, 2012 at 2:57 PM, Sudarshan Raghavan
<[email protected]> wrote:
> While running a CPS test of 330 connections per sec on a https server
> (non blocking sockets and built with openssl 1.0.1c) I am able to see
> high CPU usage when running on a 32 bit system (i686) while the 64 bit
> version of the same application does not show abnormal CPU usage. Both
> the 32 and 64 bit systems have the same configuration of quad-core AMD
> Opteron with 4 GB of RAM.
>
> 32 bit system and binary: 360 - 370% CPU usage
> 64 bit system and binary: 90 - 95% CPU Usage
>
> I ran oprofile on the 32 bit system and this is what I see in the output
>
> CPU: AMD64 family10, speed 2211.25 MHz (estimated)
> Counted CPU_CLK_UNHALTED events (Cycles outside of halt state) with a
> unit mask of 0x00 (No unit mask) count 100000
> samples  %        app name                 symbol name
> 9470703  90.2941  libcrypto.so.1.0.0       bn_mul_mont
> 257622    2.4562  no-vmlinux               /no-vmlinux
> 184898    1.7628  libcrypto.so.1.0.0       BN_mod_exp_mont_consttime
> 66404     0.6331  libcrypto.so.1.0.0       BN_mod_mul_montgomery
> 46807     0.4463  libcrypto.so.1.0.0       bn_mul_words
> 32781     0.3125  libcrypto.so.1.0.0       bn_sub_words
> 25144     0.2397  libcrypto.so.1.0.0       bn_mul_add_words
> 23523     0.2243  libcrypto.so.1.0.0       sha1_block_data_order
>
> Has anyone else run into this problem? Is this a known issue?
>
> Regards,
> Sudarshan
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