[openssl-users] Performance problems with OpenSSL and threading

Thu Apr 23 23:46:23 UTC 2015

Looking at your call stack, it appears you're testing with FIPS mode
enabled.  There's a lock in FIPS_selftest_failed() that's used to ensure
the crypto algorithms inside the FIPS boundary are not utilized until
after the POST has completed and passed. Unfortunately this lock remains
installed for the lifetime of the process.  We've seen thread contention
in this area when using OpenSSL.  One work-around is to modify your
handler that you pass to SSL_locking_callback() to not lock when the
lock ID is CRYPTO_LOCK_FIPS.  But you would only want to disable this
particular lock ID after the POST has completed.

If the above doesn't help, another item to check is whether you're
instantiating an SSL_CTX for each thread.  I've seen some developers use
a single SSL_CTX for multiple threads.  This results in a single
instance of the server cert and private key being shared across all the
threads.  This results in thread contention on the asymmetric key
operations associated with the cert and private key (e.g. RSA).  Be sure
that each thread instantiates it's own SSL_CTX and certificate/private key.

Lastly, add some debugs to count the locks by lock ID in your lock
handler.  There are about 40 different lock IDs defined in
crypto/crypto.h.  You'll need to identify which lock is causing the
thread contention.  Once you know that, then you can look in the code to
see where that lock is used and troubleshoot from there.

On 04/23/2015 07:23 PM, Bryan Call wrote:
> I was running a benchmark on a 28 core (56 hyper-threaded) server that
> is running 84 threads in the process and I am seeing a lot of lock
> contention.  I saw a lot of lock contention in the calls to
> SSL_get_error() ssl3_accept().  I am running RHEL 6.5
> and openssl-1.0.1e-30.el6_6.7.x86_64.  We have
> used SSL_locking_callback() to setup pthread mutex locks, but haven’t
> setup dynlocks yet.  Would dynlocks help in this scenario?
>
>
> Output from perf:
> Samples: 1M of event 'cycles', Event count (approx.): 602783506611
> - 48.04% [ET_NET 0] [kernel.kallsyms] [k] _spin_lock ◆
> - _spin_lock ▒
>
>   * + 48.05% futex_wait_setup ▒
>   * + 47.79% futex_wake ▒
>   * + 1.20% tcp_v4_rcv ▒
>   * + 0.98% task_rq_lock ▒
>   * + 0.64% double_lock_balance ▒
>
> + 3.94% [ET_NET 0] libcrypto.so.1.0.1e [.] bn_mul_mont ▒
> + 1.93% [ET_NET 0] libcrypto.so.1.0.1e [.] BN_usub ▒
> + 1.80% [ET_NET 0] libcrypto.so.1.0.1e [.] 0x00000000000e5200 ▒
> + 1.49% [ET_NET 0] libcrypto.so.1.0.1e [.] sha256_block_data_order ▒
> + 0.97% [ET_NET 0] libcrypto.so.1.0.1e [.] gcm_ghash_clmul ▒
> + 0.85% [ET_NET 0] libpthread-2.12.so [.] pthread_mutex_lock ▒
> + 0.84% [ET_NET 0] libcrypto.so.1.0.1e [.] aesni_ctr32_encrypt_blocks ▒
> + 0.74% [ET_NET 0] libc-2.12.so [.] malloc ▒
> + 0.72% [ET_NET 0] libc-2.12.so [.] memcpy ▒
> + 0.57% [ET_NET 0] libcrypto.so.1.0.1e [.] BN_mod_mul_montgomery ▒
> + 0.51% [ET_NET 0] libpthread-2.12.so [.] pthread_mutex_unlock
>
> pstack of the process (only a couple of the interesting threads):
> Thread 1 (Thread 0x7f1fba151800 (LWP 1106)):
> #0 0x00007f1fbaaeb264 in __lll_lock_wait () from /lib64/libpthread.so.0
> #1 0x00007f1fbaae6508 in _L_lock_854 () from /lib64/libpthread.so.0
> #2 0x00007f1fbaae63d7 in pthread_mutex_lock () from /lib64/libpthread.so.0
> #3 0x000000000072822f in SSL_locking_callback(int, int, char const*,
> int) ()
> #4 0x00000031d2ae7f03 in ?? () from /usr/lib64/libcrypto.so.10
> #5 0x00000031d2ae7d8c in ?? () from /usr/lib64/libcrypto.so.10
> #6 0x00000031d2ae80ab in ERR_get_state () from /usr/lib64/libcrypto.so.10
> #7 0x00000031d2ae8557 in ?? () from /usr/lib64/libcrypto.so.10
> #8 0x00000031d2e424a9 in SSL_get_error () from /usr/lib64/libssl.so.10
> #9 0x00000000007249ef in
> SSLNetVConnection::load_buffer_and_write(long, long&, long&,
> MIOBufferAccessor&, int&) ()
> #10 0x00000000007389df in write_to_net_io(NetHandler*,
> UnixNetVConnection*, EThread*) ()
> #11 0x0000000000738523 in write_to_net(NetHandler*,
> UnixNetVConnection*, EThread*) ()
> #12 0x0000000000731922 in NetHandler::mainNetEvent(int, Event*) ()
> #13 0x00000000004f6d48 in Continuation::handleEvent(int, void*) ()
> #14 0x000000000075877a in EThread::process_event(Event*, int) ()
> #15 0x0000000000758c84 in EThread::ex
>
> Thread 56 (Thread 0x7f1fb0ecd700 (LWP 1172)):
> #0 0x00007f1fbaae77d9 in pthread_mutex_unlock () from
> /lib64/libpthread.so.0
> #1 0x0000000000728265 in SSL_locking_callback(int, int, char const*,
> int) ()
> #2 0x00000031d2b57402 in ?? () from /usr/lib64/libcrypto.so.10
> #3 0x00000031d2b574bd in FIPS_selftest_failed () from
> /usr/lib64/libcrypto.so.10
> #4 0x00000031d2ae9f1c in EVP_DigestInit_ex () from
> /usr/lib64/libcrypto.so.10
> #5 0x00000031d2a7977e in HMAC_Init_ex () from /usr/lib64/libcrypto.so.10
> #6 0x00000031d2a79c29 in ?? () from /usr/lib64/libcrypto.so.10
> #7 0x00000031d2af7a42 in EVP_PKEY_CTX_ctrl () from
> /usr/lib64/libcrypto.so.10
> #8 0x00000031d2ae9ffb in EVP_DigestInit_ex () from
> /usr/lib64/libcrypto.so.10
> #9 0x00000031d2af952a in ?? () from /usr/lib64/libcrypto.so.10
> #10 0x00000031d2e34cf2 in tls1_PRF () from /usr/lib64/libssl.so.10
> #11 0x00000031d2e35796 in tls1_final_finish_mac () from
> /usr/lib64/libssl.so.10
> #12 0x00000031d2e2db2e in ssl3_get_message () from /usr/lib64/libssl.so.10
> #13 0x00000031d2e1dc3c in ssl3_get_cert_verify () from
> /usr/lib64/libssl.so.10
> #14 0x00000031d2e220d6 in ssl3_accept () from /usr/lib64/libssl.so.10
> #15 0x0000000000725287 in
> SSLNetVConnection::sslServerHandShakeEvent(int&) ()
> #16 0x00000000007251b3 in SSLNetVConnection::sslStartHandShake(int,
> int&) ()
> #17 0x0000000000723df3 in SSLNetVConnection::net_read_io(NetHandler*,
> EThread*) ()
> #18 0x0000000000731852 in NetHandler::mainNetEvent(int, Event*) ()
> #19 0x00000000004f6d48 in Continuation::handleEvent(int, void*) ()
> #20 0x000000000075877a in EThread::process_event(Event*, int) ()
> #21 0x0000000000758c84 in EThread::execute() ()
> #22 0x0000000000757cf8 in spawn_thread_internal(void*) ()
> #23 0x00007f1fbaae49d1 in start_thread () from /lib64/libpthread.so.0
> #24 0x00000030ff0e88fd in clone () from /lib64/libc.so.6
>
> -Bryan
>
>
>
>
>
>
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