[jira] [Created] (TS-4234) ATS on AARCH64 use spinlock for SSL locking

[Shay Gal-On (JIRA)]

Shay Gal-On created TS-4234:
-------------------------------

             Summary: ATS on AARCH64 use spinlock for SSL locking
                 Key: TS-4234
                 URL: https://issues.apache.org/jira/browse/TS-4234
             Project: Traffic Server
          Issue Type: Improvement
          Components: SSL
            Reporter: Shay Gal-On


Currently on aarch64 mutex locking can be slower then necessary under load. The 
patch below adds an option to substitute the mutex in ssl locking callback with 
a spinlock using gcc intrinsics.

diff -Nau -x Makefile -x .Tpo -x .deps 
orig-trafficserver-5.3.2/iocore/net/SSLUtils.cc 
trafficserver-5.3.2/iocore/net/SSLUtils.cc
--- orig-trafficserver-5.3.2/iocore/net/SSLUtils.cc     2015-09-08 
13:05:06.000000000 -0700
+++ trafficserver-5.3.2/iocore/net/SSLUtils.cc  2016-02-26 11:44:55.709451000 
-0800
@@ -119,9 +119,17 @@
 #endif


-static pthread_mutex_t *mutex_buf = NULL;
 static bool open_ssl_initialized = false;

+#ifdef SSL_USE_SPINLOCK
+#include "Spinlock.h"
+#define SSL_locking_callback SSL_locking_callback_spinlock
+static Spinlock *spinlock_buf = NULL;
+#else
+#define SSL_locking_callback SSL_locking_callback_mutex
+static pthread_mutex_t *mutex_buf = NULL;
+#endif
+
 RecRawStatBlock *ssl_rsb = NULL;
 static InkHashTable *ssl_cipher_name_table = NULL;

@@ -135,9 +143,24 @@
 {
   return (unsigned long)pthread_self();
 }
+#ifdef SSL_USE_SPINLOCK
+static void
+SSL_locking_callback_spinlock(int mode, int type, const char * /* file 
ATS_UNUSED */, int /* line ATS_UNUSED */)
+{
+  ink_assert(type < CRYPTO_num_locks());

+  if (mode & CRYPTO_LOCK) {
+       spinlock_buf[type].lock();
+  } else if (mode & CRYPTO_UNLOCK) {
+       spinlock_buf[type].unlock();
+  } else {
+    Debug("ssl", "invalid SSL locking mode 0x%x", mode);
+    ink_assert(0);
+  }
+}
+#else
 static void
-SSL_locking_callback(int mode, int type, const char * /* file ATS_UNUSED */, 
int /* line ATS_UNUSED */)
+SSL_locking_callback_mutex(int mode, int type, const char * /* file ATS_UNUSED 
*/, int /* line ATS_UNUSED */)
 {
   ink_assert(type < CRYPTO_num_locks());

@@ -150,6 +173,7 @@
     ink_assert(0);
   }
 }
+#endif

 static bool
 SSL_CTX_add_extra_chain_cert_file(SSL_CTX *ctx, const char *chainfile)
@@ -758,11 +782,14 @@
     SSL_load_error_strings();
     SSL_library_init();

+#ifdef SSL_USE_SPINLOCK
+    spinlock_buf = new Spinlock[CRYPTO_num_locks()];
+#else
     mutex_buf = (pthread_mutex_t *)OPENSSL_malloc(CRYPTO_num_locks() * 
sizeof(pthread_mutex_t));
-
     for (int i = 0; i < CRYPTO_num_locks(); i++) {
       pthread_mutex_init(&mutex_buf[i], NULL);
     }
+#endif

     CRYPTO_set_locking_callback(SSL_locking_callback);
     CRYPTO_set_id_callback(SSL_pthreads_thread_id);
diff -Nau -x Makefile -x .Tpo -x .deps 
orig-trafficserver-5.3.2/iocore/net/Spinlock.h 
trafficserver-5.3.2/iocore/net/Spinlock.h
--- orig-trafficserver-5.3.2/iocore/net/Spinlock.h      1969-12-31 
16:00:00.000000000 -0800
+++ trafficserver-5.3.2/iocore/net/Spinlock.h   2016-02-26 11:34:06.359451000 
-0800
@@ -0,0 +1,38 @@
+/** @file
+
+Author: Shay Gal-On
+
+A class implementing a simple spinlock using GCC atomics,
+using sched_yield while lock fails.
+
+*/
+
+#include <sched.h>
+
+class Spinlock
+{
+public:
+    int _data;
+
+public:
+    bool try_lock()
+    {
+        int r = __sync_lock_test_and_set( &_data, 1 );
+        return r == 0;
+    }
+
+    void lock()
+    {
+        for( unsigned k = 0; !try_lock(); ++k )
+        {
+                 sched_yield();
+        }
+    }
+
+    void unlock()
+    {
+        __sync_lock_release( &_data );
+    }
+};
+
+




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