[openssl-users] Performance problems with OpenSSL and threading

[Bryan Call]

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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