OpenSSL 1.1.1g Windows build slow rsa tests

[Dan Heinz]

-----Original Message-----
From: openssl-users <openssl-users-bounces at openssl.org> On Behalf Of Michael Wojcik
Sent: Thursday, January 21, 2021 9:28 AM
To: openssl-users at openssl.org
Subject: RE: OpenSSL 1.1.1g Windows build slow rsa tests

> >From: openssl-users <openssl-users-bounces at openssl.org> On Behalf Of 
> >Dr Paul Dale
> >Sent: Wednesday, 20 January, 2021 19:28
>>
>> I'd suggest giving a build without the no-asm option a try.  The 
>> performance difference is usually quite significant.

>I agree. It just doesn't explain what Dan's email claims.

>> Statis vs dynamic builds wouldn't normally be associated with such a 
>> large difference.  If the difference were routinely this large, nobody 
>> would use dynamic linking.

>In this case it's the static-linked version which is slower. But I'd be surprised if that's actually the cause.

Thank you all for the helpful suggestions.  When I removed no-asm and built using nmake in the Developer Command  Prompt for Visual Studio 2015, I ended up getting an error "VC-WIN64A X86 conflicts with target x64".  From the command prompt I ran cl and saw this "Microsoft (R) C/C++ Optimizing Compiler Version 19.00.24215.1 for x86".  So I was building for x86?  I'm not sure why it built with no-asm, but it did.

Once I ran the correct command prompt (I used Visual Studio x64 Native Tools Command Prompt), I saw a huge speed increase.  For example, 2048 bits:
Doing 2048 bits private rsa's for 10s: 8384 2048 bits private RSA's in 10.02s
Doing 2048 bits public rsa's for 10s: 236090 2048 bits public RSA's in 9.98s

Previously, I saw:
Doing 2048 bits private rsa's for 10s: 409 2048 bits private RSA's in 10.00s
Doing 2048 bits public rsa's for 10s: 15663 2048 bits public RSA's in 10.02s

For further testing, I added back no-asm and my speed tests were in line with the downloaded openssl binary I was testing with.  
Doing 2048 bits private rsa's for 10s: 1868 2048 bits private RSA's in 10.00s
Doing 2048 bits public rsa's for 10s: 71338 2048 bits public RSA's in 10.02s

You can see removing no-asm does make a pretty large speed increase too.

In summary, using the correct build tools helps (although I am surprised it built with no-asm).  And removing no-asm sped things up.