First, it seems to be busy-looping when calling SSL_connect(). Second, it only calls SSL_read() when the socket is readable and only calls SSL_write() when it is writeable. However, SSL_write() can be blocked for reading, for example during renegotiation (see manual page).

This is a problem because this example is one of the first result when looking for openssl epoll with some search engines.

https://github.com/mdaxini/howto-openssl/wiki/OpenSSL-Cipher-Speed

The openssl manual notes: https://wiki.openssl.org/index.php/Manual:OPENSSL_ia32cap(3)
OPENSSL_ia32cap:
bit #33 denoting availability of PCLMULQDQ instruction;
bit #57 denoting AES-NI instruction set extension;

Disabling both results in different performance between having AES-NI on and off in the BIOS.

The difference is not noticeable in aes-128-cbc, but is in other algorithms:

== Disable Both AES-NI and PCLMULQDQ ==

OPENSSL_ia32cap="~0x200000200000000" openssl speed -elapsed -evp aes-128-cbc

AES-NI ON: 363 MB/s
AES-NI OFF: 363 MB/s

OPENSSL_ia32cap="~0x200000200000000" openssl speed -elapsed -evp aes-128-gcm

AES-NI ON: 260 MB/s
AES-NI OFF: 260 MB/s

== Disabled only AES-NI ==

OPENSSL_ia32cap="~0x200000000000000" openssl speed -elapsed -evp aes-128-cbc

AES-NI ON: 363 MB/s
AES-NI OFF: 363 MB/s

OPENSSL_ia32cap="~0x200000000000000" openssl speed -elapsed -evp aes-128-gcm

AES-NI ON: 516 MB/s
AES-NI OFF: 516 MB/s

== Normal ==

openssl speed -elapsed -evp aes-128-cbc

AES-NI ON: 768 MB/s
AES-NI OFF: 363 MB/s

openssl speed -elapsed -evp aes-128-gcm

AES-NI ON: 3315 MB/s
AES-NI OFF: 516 MB/s

As you can see, under aes-128-gcm, disabling the additional instructions, rather than just AES-NI, cuts performance in half.

I try some modification:

• SSL_write(ssl, "Host www.google.com\nGET /\n\n", strlen("Host www.google.com\nGET /\n\n"));
• SSL_CTX_set_verify(ctx, SSL_VERIFY_NONE, 0);

And part of the reply is lost. I receive the first 1239 of the 1555 or more size.